7.) When I've captured my adversary and he says, "Look, before you kill me, will you at least tell me what this is all about?" I'll say, "No." and shoot him. No, on second thought I'll shoot him then say "No."
7.) (Depending on what site you're using) When the rebel leader challenges me to fight one-on-one and asks, "Or are you afraid without your armies to back you up?" My reply will be, "No, just sensible."
11.) I will be secure in my superiority. Therefore, I will feel no need to prove it by leaving clues in the form of riddles or leaving my weaker enemies alive to show they pose no threat.
39.) I will be neither chivalrous nor sporting. If I have an unstoppable superweapon, I will use it as early and as often as possible instead of keeping it in reserve.
I will only employ assassins and bounty hunters that work for "the money". Those who work for "the thrill of the hunt" tend to do stupid things, like even the odds to give their victim a sporting chance.
If I'm sitting in my camp, hear a twig snap, start to investigate, then encounter a small woodland creature, I will send out some scouts anyway just to be on the safe side. (If they disappear into the foliage, I will not send out another patrol; I will break out the napalm.)
201.) Under no circumstances will I ever, EVER give a weapon back to the hero engaged with me in a duel. Sporting chances are for sissies.
In The Gamer's Alliance, several heroes and villains fight dirty whenever they can; very few characters actually try to fight in a gentlemanly manner.
Sensei Ito, one of the martial arts instructors at Whateley Academy in the Whateley Universe, has created an entire fighting style around this. He's a little old man with no mutant powers, and he can take down flying bricks, avatars, you name it. He's fighting (and training) mutants, so you know he isn't going to fight fair.
One should note, of course, that some folks - including Ayla - doubt that Ito is actually just a Badass Normal. One of the prevailing theories is that he's also either a secret mutant, or very experienced at Ki manipulation. Odds are weighted towards the Ki manipulation.
Erik Mahren, before his emergence as a mutant. As one of the range instructors, he's the one who okays or used to what is and is not allowed to be used on the range. And he is a Badass Normal, and is more than capable of defending himself against most of the students at Whateley - even the ones who think it's funny to sneak up behind people and stab them in the kidneys.
Most villains, and plenty of heroes, are like this; Mephisto even explains that most of the 'narrow escapes' heroes have were actually planned as part of a Kansas City Shuffle, and that when villains really wanted their opponents dead, they ended up dead. Pretty much the only supervillain who doesn't kill is Mimeo, and he has an ulterior motive for that. Conversely, 'heroes' like the Dark Avenger, the Lamplighter, and Jack Rabbit are quick to put down their opponents in a permanent fashion, and even the Big Good of the series, Lady Astarte, sees Thou Shalt Not Kill more as a preferred outcome than a rule.
In The Salvation War, the demons accuse the humans of fighting dishonorably by using long-ranged artillery, airstrikes, tanks, and long-range rifles rather than fight the demons in hand-to-hand combat. Or at least, the demons try to, but the humans are too busy slaughtering their Bronze-Age armies wholesale to listen.
Of course, the demons' view on "honorable" combat is for humans to be crushed under their heels before becoming dinner.
Pretty much everyone in Darwin's Soldiers fights dirty but Dr. Kerzach probably fights the dirtiest.
In Suburban Knights, the That Guy with the Glasses crew tries to play along the fantasy scenario, only using (fake) swords. But when the Cloaks use a machine gun, Angry Joe uses his gun. And in a climactic battle, Linkara goes "screw this" before dropping his sword and grabbing his gun, and while Joe is using his SMG again, Obscurus Lupa grabs a spare and starts shooting as well.
Darth Apparatus from The Gungan Council, a Sith, has thrown sand in eyes, used blasters, and bombs in order to win in a universe where his comrades will use only the Force and their lightsabers.
Rym of the podcast Geek Nights has repeatedly stated he is one. People still vote for him in political games, anyway.
"YOU PLAY TO WIN THE GAME!"
Alexis of A Grey World won't shy from doing what needs to be done to survive a fight.
Psycho Gecko of World Domination in Retrospect proclaims a fair fight to be the last act of a desperate man. He'll hide behind illusions, make use of deadly or incapacitating chemicals, hit any weak point he can find on a body, and will use anything as a weapon that he can get his hands on. He also keeps a mini-chainsaw called the Nasty Surprise hidden under one arm.
Given that Worm takes place in a Crapsack World of superheroes and supervillains, a couple characters develop a "whatever works" attitude towards combat:
Agent Washington of Red vs. Blue is a freelancer with no AI and no special combat abilities (sans amazing capability with firearms) or armor enhancements. He makes up for this by fighting smart. He always tries to even the odds through strength in numbers, stealing weapons off his enemies, or just grabbing a bigger gun (sometimes metaphorical, sometimes not). He was able to stop The Meta (an absurdly powerful hivemind of AI in a super strong, over-enhanced Blood Knight) not through force, but with deception and knowledge he himself wasn't supposed to hold about his surroundings.
Agent Tex is the strongest combatant in the series, but still prefers a pragmatic fight. She often uses her cloaking device and plasma grenades to end a fight before she starts it, and will set up a battle field with explosives and extra weapons ahead of time. She'd probably win more if she wasn't subconsciously programmed to be a Failure Hero.
Yang Xiao Long. In her introduction, she steps into a Bad-Guy Bar and gets into an altercation with the owner, a big mafia boss. When he threatens to sic his goons on her, she sweet-talks him and offers a make-up kiss. When the schmuck acquiesces to her offer and leans in to plant a kiss onto the lovely blonde, she plants an altogether different kind of kiss onto him. She also qualifies if you bear in mind that when Ruby, Weiss and Blake aren't using their weapons they store them in rocket-powered lockers at Beacon, ready to call in whenever they need them. Yang? Her EmberCelica folds up into a pair of unassuming bracelets, so she can take them anywhere and lay the smack-down any time she needs to.
Her sister, Ruby Rose also qualifies. When fighting weaker opponents her fighting style is pretty straightforward, but when things are serious she's one third The Strategist, one third this and one third Crazy Awesome. On this trope's side she's not afraid to use freezing bullets, taking someone else's weapon when her own is unavailable, blinding opponents with tricks like pulling hat over his eyes or making them lose balance by opening enemy's umbrella during windy fight on top of airship.
In "Punished", we learn these two probably got this trait from Uncle Qrow. For one thing, he freely abuses his Semblance (The Jinx) to cause problems for his opponent, and when Tyrian disarms him of his sword, Qrow settles for simply beating the shit out of the maniac with his bare fists, which stuns and shocks Tyrian long enough for Qrow to retrieve his weapon.
On bad guys side there is Roman Torchwick with cane that works as a gun and Grappling-Hook Pistol. He doesn't hesitate to deliver shoting equivalent of sucker punch when enemy is distracted or shot down heavy container on top of enemy's head.
Spoony once told the story of his Star Wars RPG character that killed Sith with a number of dirty tricks. Things like flamethrowers, shotguns, and rigging his ship with explosives.
A convention D&D game guest starring Linkara and Mike "The Birdman" Dodd had Spoony's character grab a glass during dinner, shatter it and put the shards in his satchel. When the party is beset upon by a big, hulking brute of a monster later on, Spoony just throws GLASS IN ITS EYES.
When he finished his review of Final Fantasy XIII, when Snow came to fight him, after assuring him that he would fight fairly, he immediately opened fire with automatic firearms. When that doesn't work, Spoony ultimately wins by ripping his throat out with his bare hands.
When a Headless attacked him after one of his Ultima reviews, Spoony claimed that Linkara would probably be all "I AM A MAN!" and fight him like a man. Then Spoony kicks the Headless in the crotch, and remarks that he on the other hand fights like a dirty bastard.