Sebastian Michaelis from the above image is this trope. He could have written this trope all on his own, and made you tea and a five-star, nine course banquet in the meantime.
Grell Sutcliff was a temporary one for Madame Red.
Yet another is Agni, super-powered servant to a very spoiled Indian prince.
And then there's Ash, the queen's butler. In the manga, she has two butlers; Charles Grey and Charles Phillips, AKA "Double Charles".
The Phantomhive servants, though quite behind Sebastian, are still very lethal. We have Maylene the Ninja Maid, who is able to snipe with PISTOLS while leaping from rooftop to rooftop; Finnian, who is extremely strong (to the point of a monster); Tanaka, who effortlessly manages to kill an enemy right outside of Elizabeth's room (without a drop of blood on his clothes (he says that he knows Baritsu in a later chapter); and Bard, who, though weakest in strength, made up for it with tactical knowledge and killed the enemy with a flour bomb. When Ciel warned not to look down upon the Phantomhives' servants, he means it.
Though neither a butler, nor a skilled fighter, Nike in Appleseed fits this trope quite well. It's easy to underestimate her as Prime Minister Athena's loyal secretary. But even for a Chief of Staff, she seems to be holding enormous executive powers on her own and having Athenas full confidence. The fact that she's The Stoic and could pass as a Bifauxnen without problems certainly helps her appearing as The Dragon.
Baccano! has three of them, played with varying levels of straightness: Christopher Shouldered is the most simple and straightforward example, serving as Ricard Russo's bodyguard out of gratitude for saving his life. Chane Laforet is a little more complicated, as she was an almost disturbingly loyal servant of her manipulative father up until her run-in with Claire Stanfield, after which she finds herself fretting the inevitable Friend or Idol Decision. Ennis is a subversion — she initially fits all of the characteristics of a typical Battle Butler for Big Bad Szilard Quates (up to and including wearing suits and serving as his driver), until she gets the opportunity to voice her thoughts: she serves him only because he can kill her with a single thought if she doesn't, and hates him more than anyone else does for the things he makes her do.
Roger Smith's manservant Norman in The Big O. In addition to making soup and cleaning the house, he's quite handy with a machine gun and drives a motorcycle with a rocket launcher in the side car. To stress how badass Norman is, one need only look to the Christmas episode. Roger, mid-fight, asks Norman to get his dry-cleaning. Norman accomplishes this by taking his motorcycle and driving it through the building without slowing down. Not only did he grab the laundry, he got a date on the way out. And then there's this one time in the second season when the Smith house is under attack, Norman responds with heavy artillery and exquisitely delivered profanity.
Norman: "Sons of bitches!"
Pandora Hearts gives us Gilbert, Oz's servant and best friend, who is very efficient at protecting his master. Then there's Sharon's servant Break, who was also a knight serving a noble family in the past. We also have Echo to Vincent, the Baskervilles to Glen, and the Nightray servants to their respective masters.
Sayoko Shinozaki from Code Geass, though her case is something of a subversion. Though she exhibits an understandable protective streak towards Nunnally, she aids the terrorist Zero without realizing that he's actually Nunnally's older brother Lelouch. In addition, she has yet to exhibit it, but the writing staff has repeatedly hinted that she may turn out to be as impressive a fighter as the beyond-human Suzaku. And all this due to her runaway popularity with the audience.
Riff/Riffael of the Hargreaves family in Count Cain.
Watari, L's butler of Death Note fame. Can prepare delicious sweets for L, while capable of maintaining the facade that he is the aloof detective, and can take you down with a single, steady shot from a sniper rifle while dangling from the legs of a flying helicopter. He's also revealed to have raised L from very early childhood, which probably explains his personal devotion.
In Digimon Adventure 02, Wormmon acts as a (not especially useful) Battle Butler for Ken, getting nothing but insults and whippings in return. Ken comes to regret abusing Wormmon, though, after he performs his Heel Face Turn.
Otose, the battle maid in Domina No Do. Her character design can be summarized as "Female Big Boss."
Space Butler from Excel Saga, who serves the Puchuus mainly because he cannot resist their illusory cuteness.
Juubei from Get Backers has a brief angst fit because his duty in life was basically to be Kazuki's Battle Doctor, but Kazuki left, and he's since sworn himself to Makubex, who previously ordered him to kill Kazuki in what he admitted was a test of loyalty. In the end, he balances his dual loyalties nicely.
Both Kirishima Shinobu and Hosaka Mitsuru of Goshuushou Sama Ninomiya Kun are Battle Butlers to their ojou-sama Houjou Reika. Both demonstrate extreme devoutness, top-notch martial skills, and protective behavior towards Reika.
Yuki Nagato from Haruhi Suzumiya acts like this for Kyon, more or less placing him above anything else. Her loyalty ultimately lies with him, even above that of her boss and Haruhi. Sometimes it seems like she will only do something when Kyon tells her to. And boy, don't you dare to threaten Kyon, or she'll kick your ass hard. Then again, Kyon doesn't really play the role of her "master." In fact, he tries to avoid relying on her help, feeling it unfair to let her do all the dirty work, just because she won the Superpower Lottery.
The eponymous Hayate is a unique look into a newly-minted Battle Butler; his loyalty initiated by a massive debt. He's had more experience in the area than that would lead one would think, however. He was trained in butlering as a small child by someone who is either a very powerful mage or a goddess.
Also, Segawa Kotetsu of the Segawa household, Machina (Athena's servant), Kaede Nonohara of the Azumamiya household, Himuro Saeki of the Ookouchi household as well as Ichijou as Mikoto's butler. Almost makes you think the series runs off of this trope, doesn't it?
Despite the series name, Hayate himself seems less of a Battle Butler than the others.
Perhaps in the anime where the other butlers get to fight more and the chapters where Hayate fights tend not to be included. But in the manga Hayate is both an expert with domestic skills, including being Crazy-Prepared for anything Nagi could possibly need at a moment's notice, but is also an excellent fighter who has defeated robots, the yakuza, giant tree things, the mafia (in Greece!), large mecha, other butlers, ginormous robots, etc. He's referred to as a Gundam-made-flesh for a reason.
Walter C. Dolnez/Dornez from Hellsing is a rather literal example. Not only is he incredibly badass and able to kill armies of vampires with his Razor Floss since he was 14 years-old, but his devotion to Integra and the British crown is unquestioned. Until his still questioned Face Heel Turn, making him some kind of Blood Knight or so..
Walter: Hello, my name is Walter C. Dornez, ex-vampire hunter and butler to the Hellsing Organization. I answer the door, I clean up the estate, and I take outthe trash. And I also kill self-entitled little twats like yourself.
From Higurashi No Naku Koro Ni Kai we have Kasai. With his occasionally Yandere client Shion and Doctor Irie, he breaks into a hospital filled with secret conspirators. He then gets to show off his skills with a shotgun including smacking some guy in the face with one after interrogating him. He is later shown shooting out the tires of a van with a sniper rifle
Half the cast in Inu X Boku SS: Miketsukami, Yukinokouji, Karuta, Natsume. Interestingly, for the most part their masters (except Watanuki) are even more battle-capable.
Vanilla Ice in JoJo's Bizarre Adventure. He's so faithful to Dio that when Dio asks him to slice off his own head, he proceeds to do so with no hesitation. He got better.
Kogarashi, the title Maid Guy in Kamen no Maid Guy. He's a large, musclebound masked man, and the fact that he's wearing a dress only makes him that much more terrifying to any who meets him.
Paul Moriyama in Keroro Gunsou is Momoka's butler, seemingly charged with caring and protecting her. He is also alluded to be massively powerful, and in the manga it's hinted he's a veteran of World War II. See this video at around 0:16. Paul has a very impressive musculature.
Escargoon, Dedede's butler/servant/secretary from the Kirbyanime is often described as a Battle Butler. While he doesn't engage in close combat with any effectiveness (even Dedede can best him in that department), he's often seen leading the troops and managing the combat machines.
Last Exile presents Dio of the Noble House of Eraclea, whose friend and combat butler Luciola acts as his loyal bodyguard up to the point of giving himself up to Dio's sister, Maestro Delphine, so she allows Dio to escape. He has no regrets as he calmly accepts a ring that immediately kills him.
Jodo from the second Lupin III movie, The Castle Of Cagliostro diligently serves the Count, even serving as one of the his ninjas and taking down Zenigata's stolen autogyro and Lupin himself with a rooftop-mounted machine gun. At the end, he asks Goemon to kill him, since he has no purpose but to serve the (now-dead) Count.
Tachibana, from Mahoraba, is instantly recognizable as a member of this trope. She also qualifies as a Ninja Maid due to her ability to suddenly materialize in rooms, though.
Ostia's Governor General, Kurt Godel seem to have one of those.
Not a butler, per se, but Mikoto Minagi from Mai-HiME plays Battle Butler to two different characters. First, she's Mai's faithful sidekick (whom she likesverymuch), and later she becomes one for her brother, who has the soul of the series' Big Bad living inside him. Despite her conflicting loyalties, she swears to protect them from anything that gets in her way...and boy, can she ever.
Both Subaro and Nagare in Mayo Chiki are better fighters than pretty much anyone else in the series.
The Dark Lovers from Mermaid Melody Pichi Pichi Pitch; as their name implies, they represent different types of false love, and are all obsessed with their Master, Gackto (Gakuto if you prefer the scanlations, Gaito in the anime). Of course, he turns out to have just as intense loyalty to Sara with the exact same reason, which is the whole reason he wanted to destroy the world in the first place.
Miami Guns parodies this trope with Jii, faithful servant to Yao's father and exaggerated Badass.
Big Blue from the Monster Rancher anime. Big Blue is fiercely loyal to Pixie, protects her without a second thought, and near the end of the series he fuses his own life force (sacrificing himself) with hers to prevent her from becoming a lost disk.
In Pokémon Special, the Berlitz family's old butler, Sebastian, shows a reasonable amount of battling skill when he thinks Dia is an intruder on the estate. You really can't blame him for being a bit paranoid after what recently happened to his masters.
Canon Foreigner Sasuke Sarugakure is the Kunō Family's devoted, albeit grossly inept, ninja butler in the anime. He was conceived as a filler character, who was given most arcs involving Gosunkugi. All of them except the magic paper dolls, if memory serves. However, he became his own unique character pretty quickly.
The very first filler in the anime also has an elderly, childless rich couple try to adopt P-chan/Ryoga, and when Ranma (reluctantly) tries to retrieve him, the three butlers/servants chasing him promptly pull off their bowties and reveal martial artist weapons, much to Ranma's shock. The abridged series lampshades this trope. It was also probably the most well-animated and choreographed fight of the whole season, despite how short it was.
Slayers: Jilas is Gravos's Battle Butler. Interestingly, he outlives his master.
Mr Tanaka, butler to the Thorndyke family in Sonic X, though he's not always entirely effective when it comes to defending his employers' honour, you have to give him points for effort (and self judgement when he thinks he's failed).
In Soul Eater Noah has Gopher, a young (may or may not be an artificial creation) minion who serves Noah unquestioningly. So far unsuccessfully, but he's determined, at least. Mosquito is a clearer example, being Arachne's Battle Butler. And he's a far more effective one beating Kid rather brutally before getting owned by his Defence Mechanism Superpower. Both are devoted to their respective masters.
Taijir from They Are My Noble Masters is a loyal butler, and a retired mercenary. A flick from his finger has enough force to send Ren into solid rock. Oh, he can also do Ki attacks.
Tomoe from Kamisama Kiss is Nanami's familiar; which pretty much means his main job is to look after her basic needs. He cooks her meals, does the laundry and maintains the shrine they live in. He is also a Kitsune, implied to be one of the most powerful demons around, and he makes sure that anybody who threatens Nanami never does so again.
Alfred Pennyworth, essentially Batman's Batman. Not exactly a battle butler, but his skill at espionage and disguise rivals Batman's, and as a retired secret agent he knows his way around a shotgun. A former combat medic, he's also a skilled surgeon, and has served as Batman's private physician over the years (just think how tough that job must be...)
Alfred, being a loyal Battle Butler, accompanied Bruce Wayne as he tracked Bane and his thugs during the events of Knightfall — and then, when Bruce refused to obey his doctor's orders (or risk being completely paralyzed), he resigned from Wayne's service entirely.
From the same movie series, it's also stated that he's seen combat experience in Burma with the SAS. Battle Butler indeed.
So basically Alfred is James Bond in his retirement years.
From the Elseworlds story "Dark Allegiances" by Howard Chaykin comes this magnificent exchange:
Wayne: Do I want to know how you found this out — and should I be concerned about any jealous husbands? Alfred: You insult me, sir. Her husband was out of town.
In one issue of Batman: Gothic, Gotham City is overrun by homeless cultists. Batman and Robin are picked up from their hiding place by Alfred in the Bentley. When Batman asks whether Alfred had any trouble getting to them, Alfred replies "None sir." and holds up a pistol. To put it another way, Alfred is Battle Butler incarnate.
Note also that if any other member of his team were to carry a gun, Batman would most likely fire them on the spot. But Alfred is the exception. Why? Because Bruce needs him more than any of the others. (Also possibly because Alfred's so much older.)
Probably the latter. Modern portrayals of Alfred generally show him as an ex-military badass, but he's old and doesn't have the physical combat skills the rest of the Bat family do.
In a flashback sequence in the House of Hush storyline in Streets of Gotham, Alfred is shown singlehandedly stopping an attempted hit on Leslie Thompkins.
In the Booster Gold series, Booster goes back it time to the early days of Batman; when he goes to the Batcave he's repelled by Alfred using a rifle
And in Superman/Batman, guarded the cave with a shotgun.
Michael Caine portrayed his rendition of Alfred in the Nolanverse as if he were a retired SAS operative.
Alfred is tamer in The Batman, but he does have his moments, usually in episodes involving the Penguin. A backstory on the show says that Alfred's (presumably deceased) grandfather was a butler for the Cobblepots (who he described as "obnoxious snobs") who treated him like dirt and then fired him. Naturally, Alfred does not like the Penguin at all, and tends to do anything he thinks can help Batman when the villain shows up.
He's portrayed as a much more active character in Beware The Batman, and actually helps Batman in his war on crime in a more physical capacity. The writers of the show specifically drew the comparison to a retired James Bond.
The not-very-useful British comic hero Red Star Robinson only really cut it as a hero because of his robot bodyguard Mr. Syrius Thrice who was much more powerful. Thrice was dressed as a gentleman's gentleman and had proper Jeeves/Crichton manners but had powers Batman would envy.
Manute from Sin City fills this role for Ava Lord in "A Dame to Kill For" and for mob boss Wallenquist in "The Big Fat Kill."
Cadbury, butler to Richie Rich and the Rich Family, has a skill set large enough to qualify him for the mask and cape crowd.
And did as Crashman, partner to Rippy (Richie) in the 1970s comic, Super Richie.
Bryan Hand from Ms. Tree. Mr Hand was officially employed Mike, Jr.'s tutor. However, Mr Hand is also a former SAS trooper and ex-mercenary. Michael hired him because he could double as Mike, Jr.'s bodyguard; a function he performed frequently throughout the series.
Tyler, Largo Winch's butler during the Venise arc of the young milliardaire's adventures. Ten pages or so after his introduction, he impales a mafioso sent after Largo with a parasol. Largo notes that despite being an uptight Englishman in his sixties, Tyler can save his life twice, shoot four men and quote Chateaubriand in a single day of work. Tyler's martial prowess come from the fact that he is a retired British soldier hired by Robert Cotton to spy on and manipulate Largo.
The extreme end of this trope is seen in The Living Daylights. At a British Intelligence safehouse where a KGB defector is being held, everyone from gardeners to butlers is a hidden guard. One of them (callsign "Green 4") actually puts up a serious fight against Necros.
Stonewall Jackson's personal slave in Gods And Generals. Sadly Jackson feels so dependent on him that he can't quite bring himself to free him. In a way he seems almost enslaved to his slave.
Alfred from The Dark Knight mentions that he used to be a soldier and once burned a whole forest down to catch a bandit. However, he's never seen in a combat situation in the films.
He knocks down one of the intruders from behind in the burning mansion in Batman Begins.
John Woo movies A Better Tomorrow II and Hard Boiled both feature a version of the battle butler. In A Better Tomorrow II, the servant - hitman Chong is given a pile of cash by his terrified employer, but completely ignores it, indicating that his only concern is finding a Worthy Opponent.
Paul "Dibbs" Plutzker of 1995 film: Casper. He acts as Carrigan Crittenden's personal bodyguard. "Don't come near me, you spiteful spook, or I'll knock you into the next world".
Alfred in Hudson Hawk, who serves the villainous Mayflowers.
In Transformers: Dark of the Moon, Simmons gets one with Dutch, who while usually somewhat neurotic and effeminate proves to be quite dangerous if pushed.
Both the Great Leslie and Professor Fate have one in The Great Race: Hezekiah Sturdy for Leslie and Max Meen for Fate.
Cadbury from Richie Rich. When the villains send an assassin to make it look like he committed suicide, Cadbury ends up making quick work out of the assassin and breaks out of prison.
Inverted in the Pink Panther films by Cato, Clouseau's manservant. An expert in martial arts, Cato spends nearly all his time launching sneak attacks on his master, in order to keep him prepared for a real attack.
The various personal servants in Duumvirate often fit this trope, especially if they're genetically engineered. Subverted in that the master might be even more physically dangerous.
It should be noted that the series begins by exploring the possibility that the word "butler" is derived from the Fowl family's line of manservants, going as far back as the Norman conquest of England in 1066.
It gets better in Book 2.
"There were only two men on the planet better educated in the various martial arts than Butler, and he was related to one of them. The other lived on an island in the South China Sea, and spent his days meditating and beating up palm trees. You really had to feel sorry for those goblins."
It is also mentioned that a prerequisite for being a bodyguard to the Fowl family, among combat experience, is "Cordon Bleu cooking skills". And in The Lost Colony, he uses them.
To prevent Artemis and Butler from getting too close, Butler never reveals his first name to Artemis, but that didn't help. In The Eternity Code, as he's dying, he finally tells Artemis his name: Domovoi. It's very fitting, as a domovoi is a Slavic guardian spirit.
Hideo, the Tessier-Ashpools' deadly but devoted servant in William Gibson's Neuromancer, is an example of this trope.
Willikins, Commander Vimes' butler from Discworld, has quite a lot of violent capacity when his employer or city are threatened. It's explained he used to be a member of a rather vicious youth gang. He's also a member of the Ankh-Morpork City Watch "Specials", a group of would-be watchmen who, due to whatever reason, are not able to devote their full time to the job. Willikins is notable for politely downplaying in conversation his combat abilities, or even getting excessively specific when explaining why he, for example, happened to be holding a fifteen-inch icepick when a hit squad attacks the house.
More scary in that it wasn't an ice pick, but an ice knife - imagine, if you will, a breadknife, only a foot-and-a-half long, with half-inch, razor sharp serrations. That poor Dwarf.
Willikins: "My weapon of choice was a hat with sharpened pennies sewn into the brim."
Vimes: "Ye Gods, you could have someone's eye out with that."
Willikins: "With care, sir, yes."
Not to mention the time when Willikins left Vimes' service to fight in Klatch — biting a D'Reg's nose off at one point, and generally being Sergeant Badass.
It's worth noting that Vimes was glad they never met on the field of battle as kids.
Dear God, after Snuff, I will never look at Willikins the same way. Vimes himself comments that Willikins would have made an excellent copper, if only he wouldn't have made a just-as-good, if not better, assassin. The only reason why he didn't was the social class difference. That, and that assassins have rules.
Roman in the The Crown Jewels and Rock of Ages. While he'd prefer his master Maijstral be a bit more concerned with his status and honor, he is still utterly faithful and eager to pound his master's enemies into a pulp.
And do not mess with him when he's molting.
Possibly the ultimate example: Lois McMaster Bujold's Sgt. Bothari, who's taken into the Vorkosigan household as a sworn retainer after being discharged from the military on grounds of being totally bugfrak insane; he's large, paranoid-schizophrenic, sexually odd, profoundly devoted to his Lord and Lady (especially the latter), and — by the end — heartbreaking.
Pym, who (kind of) replaces Bothari, also counts. He's former ImpSec. We never see him using those skills, but I would bet good money that he hasn't lost his edge.
Also Roic, who gets to butler through battle behind Miles in Diplomatic Immunity, and has a... memorable... fight at the tail end of A Civil Campaign. We also see him in action in Cryoburn.
You could argue that Battle Butler is basically the job description for a Count's liege-sworn Armsman — most of the ones who are actual characters, rather than part of the background action, certainly qualify.
Also mentioned in The Vor Game is Sergeant Overholt, an ImpSec Non-Com that, when it's suggested that he be the batman for an AWOL Emperor Gregor of Barrayar he bemoans the fact that he hadn't gone through Illyan's "special courses", and thus, was unqualified to do so.
Adolphus Kreiger of Vampireslayer employs the powerful Roche as his manservant and leader of his minions. Kreiger hardly needs him in a fight, but he can operate during the day and is unquestionably loyal to Kreiger, as were his father and grandfather. Unfortunately, he runs afoul of his master's "mother" and gets his head ripped off
Ephant Mon from the Star Wars Expanded Universe. Despite his lack of criminal ruthlessness or selfishness, he was a loyal servant to Jabba the Hutt, and almost certainly the gangster's only actual friend. Ends up reluctantly leaving Jabba's service after trying (and failing) to get him to release Luke Skywalker.
There's also the Tac-Spec FIII Footman Droid, who such roles as chef, waiter, chauffeur, putting out the Master's wardrobe for the day with with such tools the ability to make a head-shot from 10 km away, a a high-power railgun in their arm and the strength to drive their fist through a tank. Of course, they were built in secret on a "you ask, we sell" basis for nobles and Corrupt Corporate Executive by a front company for an assassin's guild...
Of the classic "Rich Idiot with No Day Job" variety, you have P. G. Wodehouse's concoction: Jeeves — the valet to end all valets. He doesn't physically manhandle anyone, but he looks after his mental featherweight of an employer, Bertram Wooster. One can only imagine Jeeves does it simply for amusement, and there have been several fan theories on the matter.
He does get physical on one occasion when Bertie, being pursued by a policeman, ends up literally up a tree. The TV series included that scene, but inexplicably cut the line "I took the liberty of coshing the officer, sir."
And Shine Heaven Now turns him into a full-blown vampire hunting Battle Butler, though—in fact, he was the one that taught Walter everything he knew, in both the butlering and battling fronts.
Gargarey, the Peabody-Emerson's butler is a mean hand with a blackjack. The footmen are also useful in scrap and even the housemaids have learned not to scream or faint at the sight of blood.
Sarah Stevens in Dying to Please is a covert bodyguard as well as butler for her elderly boss.
Although Gunner Ferik Jurgen of the Ciaphas Cain series isn't a butler in the conventional sense, he certainly fits this trope as Commissar Ciaphas Cain's aide. He even carries out some of the typical duties of a valet when there isn't any shooting going on, such as finding accommodations, food, and entertainment suitable for a Hero of the Imperium and keeping unwelcome visitors from disturbing the Commissar's peace.
Howard Whitehouse's The Strictest School in the World and sequels include Lal Singh, "a mysterious and heroic butler."
In Honor Harrington, the personal armsmen of Grayson steadholders cover this trope quite nicely, and under Grayson law a Steadholder can have up to 50 of them. See also Cathy Montaigne's butler, a former combat-bred slave.
The Archive from The Dresden Files depends wholly on "Kinkaid", her Chauffeur, Butler and Bodyguard in one person and ex-mercenary by profession.
Belisarius Series: Rao was private tutor to Shakuntala: there is something awesome about having one of the greatest warriors in India as your Battle Butler.
In the Lord Peter Wimsey mysteries by Dorothy Sayers, Wimsey's butler Bunter was his batman in World War I.
The In Death series has Summerset. He is normally quite reserved, but has been shown to kick a little ass. Especially in flashback.
A running joke in the Ciaphas Cain series is that his batman, Jurgen, has as much or more claim on being the real hero as Cain himself. Cain acknowledges this, and is constantly annoyed that no-one else ever does.
Thomas hires one to protect Kate in The Grand Tour. Unfortunately he's rubbish as a butler, but he's an excellent bodyguard.
Fritz in the Nero Wolfe stories; although Archie is generally the muscle, Fritz has shown more than once that he is not precisely helpless when things get physical.
The domicis from The Sun Sword try to function somwhere between butler and Hyper Competent Sidekick. For many, that means being able to kick ass. Morretz is at least a bit capable of pulling this off for The Terafin, and Avandar Gallais is this to the nth degree, to the point where many have trouble understanding what the hell he's doing serving Jewel. Including Jewel, often.
Sir Lucan is probably one of the oldest examples. He actually had the title of "Royal Butler", served his king diligently, and was loyal to the end. He was also a solid and reliable knight who even nearly always survives the Battle of Camlann alongside Bedivere, living at least long enough to help Arthur off the battlefield. In one version of the legend, he even takes the role of the knight who throws Excalibur into the lake.
Live Action TV
Deneb from Kamen Rider Den-O, who's a comedic foil/caretaker to his broody partner and master, Yuto Sakurai.
You forgot to mention why he's a combat butler. Which is, of course, being able to shoot bullets from his fingers.
On Angel, Angel was paying a visit to the mansion inhabited by the Monster of the Week, and the butler attacked him on orders from his necromancer master. Angel killed him with a spoon before he could do anything but brandish some meat cleavers menacingly.
Ianto Jones, the snazzily-dressed, occasionally-asskicking (or -tasering) teaboy in Torchwood. In "Fragments", there's a flashback to when he begged Jack for a job at Torchwood, and he explicitly says, "A butler! I could be a butler!"
In Ugly Betty, Marc is Wilhelmina's Battle Butler. Disposing of the Battle Butler when it's convenient was played with when Wilhelmina "traded" Marc for something she needed for her latest scheme, but later gave it up to get Marc back. Being a Card-Carrying Villain and all, Wilhelmina refused to admit that she did this because she missed Marc, but it was still played as a Pet the Dog moment.
Kato, the chauffeur and sidekick of The Green Hornet. As played by Bruce Lee, Kato was substantially more impressive in a fight than the Hornet himself, yet remained in the humble role of a servant.
Aloysius "Nosey" Parker, servant and chauffeur to Lady Penelope from Thunderbirds, also qualifies, m'Lady.
Justified in that Parker was originally a career criminal, who first met Lady Penelope whilst he was in the middle of robbing her home. She was so impressed with his handywork, she decided to hire him instead.
Babylon 5: Lennier is this to Delenn, and Na'Toth to G'Kar.
On the Batman TV series, Alfred Pennyworth goes into action against Penguin (with his fists) and the Joker (fencing) on separate episodes.
I would count Merlin in this one, from Merlin even though Arthur never knows about it.
Higgins, Robin Masters' Major Domo in Magnum, P.I. is a former sergeant in the British Army with a complex and colorful past (though not as complex and colorful as his father's past!). However he may no qualify since there is a very good chance that he is the real Robin Masters.
Mr Bates in Downton Abbey in the backstory: he was batman (military valet; see Real Life section below) to Lord Grantham during the Second Boer War. His (extremely important) leg injury was received in that war. Bates has not had any need to physically defend Lord Grantham since then, but he has not been afraid to use his considerable physical strength on extremely rare occasions in the interests of justice.
Footman William Mason ends up in France during World War I as Matthew Crawley's batman, and dies from injuries sustained saving Matthew during the last push at Amiens.
Spoofed with Ralphus, Chris Jericho's "personal security ninja" during his time in WCW.
DiBiase's son recently went through the process of trying to recruit such a lackey, he even lampshades it by calling the position "his Virgil". After R-Truth and John Morrison turned him down, he eventually found his man... Virgil. Though their relationship only lasted a couple of months before Virgil got canned.
And, of course, later in the WWF, Triple H had Chyna, who was the rare female example that was not in Mad Love. (At least, in front of the camera...)
Changeling The Lost divides Changelings into seemings (general 'character classes' as determined by appearance and magic affinities) and kiths (specialized classes determined by the nature of the character's Durance). The Wizened seeming has the "Chatelaine" kith, for preternaturally skilled manservants and house-managers. Combine this with a fighting style (such as Kung Fu or Boxing), and BAM, instant Battle Butler.
Maid RPG has a specific set of optional rules for these: Butlers have stats superior to those that maid characters do, but have a number of restrictions as well. As battle is far from uncommon in many Maid RPG sessions, butlers have their times to shine in fulfillment of this trope, especially in defense of their respective Master characters.
Warhammer 40 K has Jurgen, battle buttler to Ciaphas Cain HERO OF THE IMPERIUM. Asides from carrying a BFG of a plasma weapon, being Cain's driver and general aide, Jurgen makes sure that Cain always has a cup of Tanna tea at hand.
Jurgen is also, due to an incredibly rare gene, a psychic null. He has no connection to the Warp whatosever, and makes even demons uncomfortable. Of course that could just be his body odour....
A rather macabre version of this appears in the Dungeon Magazine module "Horror's Havest", an adventure set in the Ravenloft setting. The Player Characters have to deal with a madman living in a mansion, where the servants (including a butler and a seemingly-harmless maid) are juju zombies, that they have to fight. (It is implied that he murdered his servants and cursed them with this condition). And dealing with this villain is only done to gain a clue about the real villain.
Rick Arrowsmith from the Visual NovelBullet Butlers, by Ocelot. A bishonen gun-wielding butler with Scary Shiny Glasses, he's unquestionably loyal to his master, Selma Fortenmayer (Which may have something to do with her role as the potential savior of the world). Interestingly enough, he's the protagonist of the game, not a side-character.
In Ōkami, a scrap of paper infused with a demon of sorts serves as "gatekeeper" to one of the game's bosses. While his only means of halting Amaterasu involve racing past her to shut gates, he has the full personality of a Battle Butler.
In the Neverwinter Nights mod series The Aielund Saga, the evil aristocrat who serves as the primary adversary in the second chapter has a capable butler who dual-wields bastard swords and attacks upon being told you are on an official investigation.
Wild ARMs 3 has Todd Dukakis, who serves as the butler of The Rival of the protagonists to the point of accompanying her and her family on treasure hunting expeditions. He is also quite good with a sword and shows his loyalty by briefly aiding the protagonists in the rescue of his master when she is abducted by another group of villains.
Todd himself is a Shout Out to Macdullen/Magdalen from the first Wild ARMs. He's literally a combat butler; he's always by Jane Maxwell's side, and while he doesn't do much battle-worthy in the original game, in the remake he uses a sword quite effectively (and will even join your party at points).
Tomoe Tachibana's head butler Hanzou.Skilled with a naginata, masters the katana to such a degree he can make a surgically-precise cut to make an airway for an operation, and can (almost) dodge arrows.
Ramirez from Skies Of Arcadia. This one showed some very insane tendencies, however; when his first Master betrayed him, Ramirez killed him and nearly everyone on his staff. When his second Master, the game's main Big Bad, is killed by the player characters late in the game, he goes into a psychotic rampage and tries to kill everything on the planet.
Sakuya Izayoi from the serves as both Remilia Scarlet's head maid and Battle Butler. In a similar fashion, Youmu Konpaku is the battle butler for the undead princess Yuyuko, although Youmu is Yuyuko's gardener, rather than her butler.
Many Stage 5 bosses are the Battle Butlers of the stage 6 ones. There is Sakuya in EoSD, Youmu in PCB, Reisen in IN, Sanae in MoF, Shou in UFO... and then Subterranean Animism totally inverts it: the Stage 5 and 6 are the pets of the Stage 4 boss.
Side note: Imperishable Night kind of has two battle butlers. Reisen, as mentioned, follows Eirin's orders in stage 5, and Eirin becomes the final boss... if you take Final A. Because, as revealed at the end of Final A and throughout Final B, Eirin is also a battle butler, to Kaguya Houraisan.
Yumeko in Mystic Square was the one who started this trend. Although, on a more general level, one could say it was actually Marisa herself who started the tradition way back in her debut in the first Touhou shooter, Story of Eastern Wonderland, being the assistant of the final boss Mima.
Death himself serves as a Battle Butler for Dracula in the Castlevania games. He's also said to be the closest thing the Dark Lord has to a friend.
Klungo from Banjo-Kazooie fits this trope perfectly; he is fiercely loyal despite being beaten (constantly) for his (constant) failures to Gruntilda the Witch. This is lampshaded late in the sequel when Klungo, after being beaten up by both his mistress and the player at least three times each, is convinced by the main characters that it's in his best interests to call it quits (and he goes off to pursue a job making "stuupid gamess," no less).
Dapang from the John Woo game Stranglehold is Wong's most loyal servant, who distinguished himself by taking some bullets for Wong during one of his death matches, crushing the would-be assassin to death with his towering strength, and then going on to kill the opponent who he was fighting while still wounded. Wong was so impressed by Dapang's loyalty that he hired him on the spot as his bodyguard.
Just about every main character in the Suikoden series has some form of bodyguard, but in the original Suikoden, the hero McDohl has Gremio, a manservant who's deft with a soup spoon and has a mean ax. And he also dies in one of the games' manyemotional moments.
Katakura Kojyuuro in Sengoku Basara is Date Masamune's butler. In real life, he might've been like this as well, seeing that he constantly watches over Masamune's well being and advises him a lot (which prevents him from reckless losses), and still gets counted as the Date clan's Power Trio.
In Fallout 3, the Mister Handy Bot is designed for domestic tasks, but does have a large saw, which has countless misfortunes laid at its feet, like your ruined birthday cake. There was actually a military version made, "Mr Gutsy", who has a flamethrower and spouts phrases that sound disturbingly like parodies of classic "Soldier Hero" talk.
Also in Fallout 3, the local radio host did a series about Daring Dashwood and his "stalwart Ghoul manservant" Argyle. It's made clear in the series that Argyle did most of the work when things got messy, which was quite often as Dashwood's mix of chivalry and womanizing got him in a lot of trouble.
You can meet the real Dashwood; he'll openly admit this was the case. He insists his own character flaws are exaggerated in the show, though.
This is actually a Shout Out to the original Green Hornet radio plays, which would've been popular in the era before The Great War.
Perhaps the best, Yes Man a semi immortal robot who is loyal only to you (because only you can get into the building we he lives) and he commands an army of highly advanced kill bots with Wolverine-like healing factors.
However you can become Mr. House's Battle Butler, Considering you can have a nuclear rocket launcher and the destructive power of the sun under your command you are kinda bad ass.
There is an actual class of Pokémon trainer called "Castle Valet" (Castle Butler in the Japanese version) in Pokemon, however it refers to Darach. Darach is implied to be the actual battler, while Caitlin just sits down watching the battle. There is also a class of trainer named "Maid".
Babus from Final Fantasy Tactics Advance. He looks like just another Nu Mou, who is serving under Prince Mewt, until you face him in battle that is. He is quite strong, magically and physically, and is 10x more dangerous when you have to fight him alone at one point.
Laurence from Ratchet & Clank: Up Your Arsenal, in a VERY weird way. I mean, Dr. Nefarious is pretty much totally incapable of accomplishing anything when he isn't around, including extermination of all organic life.
Lenny from the Shadow Hearts series. He used to be a member of the Terrible Trio in Covenant, but in From The New World, he serves as Johnny's buttler after, while tired and thirsty in the streets, being given water by Johnny many years ago. With just a phone call, he can punch an energy bomb from his fist at the enemy. From halfway across the world. Mainly because he has a contract with a demon called Godhand.
Subverted in Tomb Raider III, as your butler at Lara's Estate acts as more of a battle dummy butler. After acquiring the twin pistols, he is decked out in bulletproof padding (with his silver tray as a shield), allowing you to shoot him to your heart's content. This is most likely a reaction to people being bothered by him following you everywhere in Tomb Raider II, which led to the discovery of the "lock the butler in the freezer" exploit. The developers probably decided to throw us a bone, and go mad on him with bullets.
Rhythm Thief And The Emperors Treasure gives us Elisabeth's butler / bodyguard Alfred, who Phantom R must fight and defeat to obtain the Queen's Pendant. He's actually very competent in fighting assuming the Chevaliers Diabolique aren't involved.
Webcomic/Noblesse Frankenstein is Raizel's self-appointed butler/bodyguard/caretaker. While Raizel's fighting technique is to hit the enemy with a single swift finishing move, Frankenstein likes long, drawn-out, property damaging battles that bring out his bloodlust.
Ardsley Wooster? Gil's manservant and pretty much the Verse's James Bond analogue
Wooster's counterpart, on the other side of the Wulfenbach/Sturmvarous rivalry, is Violetta, who seems to be a much purer example of this trope. She's a Smoke Knight and Tarvek's cousin, who serves him as a joint bodyguard/trainer/butler.
Boris Dolokhov is Baron Wulfenbach's aide/secretary/administrative assistant because of his organizing skills and eidetic memory. He is also (due to some augmentation work done by his previous employer) gifted with perfect balance and hand-eye coordination, as well as two extra arms. He manages to go one-on-one with a Jägermonster and come out on top.
Also on Castle Wulfenbach there are the Lackya, "super-engineered squirrels" in pink coats who serve as footmen. Most of the time they seem to have (relatively) normal duties, but when the castle is under attack by slaver wasps, they join the clanks and Jägers to fight them off. Jägers look down on "nancy-boy feetsmen", but even they punch through rather tough constructs with bare hands.
...In fact, just about everyone who works for Klaus in a non-military capacity seems to be some version of this trope.
Geeves, valet to the royal family in the webcomic Lint, is pretty handy with a quarterstaff.
38. My personal servants will be professional bodyguards and assassins, but will dress and behave as eunuchs and maidservants. Even if I dismiss my regular guards for a "private audience" with the Hero, these personal servants (just so much furniture after all, right?) will remain in my chambers.
Maven, the administrative assistant of Selina Kyle/Catwoman.
Baby Dahl also had a Battle Butler/Nanny in her first appearance.
Owen Burnett and Preston Vogel from Gargoyles. In a subversion, Owen was revealed to be the powerful fey Puck, who created the Owen persona as a deliberate dig at Vogel. Demona briefly hired her own female Battle Butler, which promptly derailed as both secretly had their own opposing agendas. In the Slave Labor comics of Gargoyles, Thailog has Shari as his battle butler. Subverted in that she actually out ranks him in the Illuminati and she has been known to lie to Thailog from time to time.
Charles Foster Ofdensen, the manager for Dethklok in Metalocalypse. While the band thinks he's merely there to handle business and talk them out of bad ideas, he really controls everything behind the scenes, acting as an enforcer, silencer and bodyguard if need to be. When the band members were in trouble, he nearly kills the assassin in a hand-to-hand fight. He also has no qualms having undesirable people killed (Eric Jomfru) or tortured (Dr. Rockzo). When another person was considered as his replacement, Ofdensen states that he'd have to kill him to get the job. He tried. He failed. Then Ofdenson metaphorically spit on his grave by posthumously making him a pedophile.
In fact in one episode, Skwisgaar calls him "... the bests butler we's ever had..."
The show did a good job of playing up Ofdensen as being a secret Bad Ass, but he really shines as a Battle Butler when you don't see him acting. When Pickles tells him that their amazingly bad movie can't be released to the public after its first screening, Ofdensen just nods, and walks away, with no attention paid to it. A few minutes later, everyone who has laid eyes on the film (and can confirm that it sucked) is dead. Sure, it "looks" like an accident (the helicopter rotor hits the pipeline on the oil platform used for the screening as it's leaving), but you know it wasn't.
Though he usually functions as a Yes Man towards the series' villain Hordak, the character Imp in She Ra Princess Of Power also displays tendencies to function as a battle butler, most notably in the episode "Of Shadows and Skulls" wherein he attempted to force the other members of the Horde to oust Skeletor from Hordak's position. Also of note is the fact that he and Hordak tend to share a closer relationship than Hordak displays towards any of his other minions, a relationship that seems on par with the one he held for Adora and is hinted he held for Skeletor before the betrayal of the latter.
In an altenate scene of "Burns' Heir", he wields a shotgun against a robotic Richard Simmons. In the original, Burns simply closes the door on Homer. It was cut from the episode because "it often did not get a good reaction during table reads."
He was also surprisingly good at cheerfully kidnapping Tom Jones at gun point.
While not technically a butler, Hammerhead's driver in The Spectacular Spider Man didn't have any problems busting out a gun and opening fire on super powered people that went up against her boss, or using Car Fu to fight off Rhino. She is one of the coolest characters in the show and doesn't even have a name.
The same applies for her appearance in Young Justice (including the part about the skirt).
Transformers (or more specifically, Megatron) has a ton of these.
Transformers Generation 1 has Shockwave and Soundwave, both logical, level-headed, and more than willing to kick aft in Megatron's name. Soundwave even saved Megatron's life once in The Movie, though his loyalty apparently wasn't great enough to stop The Starscream and the other Decepticons from tossing him out Astrotrain's airlock five minutes later. And Shockwave even has a British accent!
Megatron: Blast that scheming spider! Again he defies me!
Inferno: Say the word, my queen, and he shall burn!
Megatron: Not just yet. And for the last time, STOP CALLING ME THAT!
Inferno: As you command, my qu...
[Megatron starts to strangle Inferno]
From Transformers Armada, Demolisher could qualify, but the real winner was Starscream of all mechs, who lost his memory in the sequel Transformers Energon. For one glorious season Megatron had the most loyal Decepticon he could ever ask for, and one who eventually followed Megatron into the Energon sun, to their mutual deaths.
Finally, Transformers Animated crosses the Battle Butler with the Yes Man in the character Lugnut. His only apparent motivation for fighting (or doing anything, really) is his undying loyalty to Megatron. Naturally, he hates Starscream, and will use his Punch of Kill Everything to pound you into the dirt for even the slightest hint of disrespect or treason.
Lugnut has two driving forces in his programming: The compulsion to serve the grand and glorious Megatron, and the utter destruction of Autobots (in the name of his glorious master).
Sicinnus was the slave of the Athenian politician Themistocles. Officially he was the schoolteacher of his children. Less officially he was the private spy.
Battle Butlers are a cliché of British military tradition. A British officer in the Good Old Days would have a soldier assigned to him, called a batman. The batman would essentially serve as the officer's servant and bodyguard. It was also customary that the batman would stay with "his" officer after said officer retired, meaning that almost all personal servants of retired officers had a LOT of military experience and pretty solid Bad Ass credentials. (THE Batman is unrelated to this trope, but Alfred would certainly qualify as a Battle Butler.)
The Russian military tradition also includes ones. The Tsarist version was called denschik (usually translated as batman), the Soviet version with a thin veneer of egalitarianism was called an ordinarets (orderly).
Generally, when a man of honour rode into battle on horseback back in the 17th century, he was usually armed with a pair of pistols, and accompanied by his servant or an subordinate, who would reload one pistol at a time when he was shooting.
Court officers and bailiffs are to be afforded far more respect and fear if they are old. Mainly because the primary source of bailiffs until they started to diversify was retired soldiers.