These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster - Surprisingly notOda Nobunaga under most respects (except a few cases in the first game). No, that "honor" goes to Fuma Kotaro, resident Ax-CrazyBlood KnightNinjaTroll who is ultimately out to cause as much havoc and suffering as (in)humanly possible. And even he is fairly rounded-out by the third game and its expansions.
Kojiro Sasaki. In Musashi's story mode he goes around assassinating officers at Sekigahara as if he was simply swatting flies. He helped start up a blood bath in a capitol city, turned two lords against one another, and all of it for his obsession with killing Musashi. There are no reasons ever given for his actions, other than, "I can kill people very well, and I like to do so.
Crazy Awesome - Hojo Ujiyasu. He'd have to be to pull off some of the insane stuff he does.
Crowning Music of Awesome - Yukimura's last stage, Siege of the Osaka Castle in SW3. Fight until Hideyori is killed by Hattori Hanzou and then listen.
Ensemble Darkhorse - Mouri Motonari. He wasn't officially revealed until one day before the release, didn't get mixed in the whole Ho Yay/Foe Yay stuff either and he is also nothing close to a Musou bishounen. Yet fan artists just love him.
In a popularity poll coinciding with Samurai Warriors 3: Empires Sakon Shima wound up being the fourth most popular character behind only Mitsunari Ishida (one of the series' most important characters), Yukimura Sanada (the poster boy), and Gracia (who probably also counts as a darkhorse).
Game Breaker - Spears in Katana can critical against nearly every enemy in the game, 1-hit-killing all but a select few of them without any stat raising.
In 2 Empires, we have the wheel formation. Not only does it give you the normal speed and morale boost if it's the better formation, but it also Doubles Your Attack And Defense, effectively turning almost any battle into a curbstompbattle if your enemy doesn't have anything to counter it (which is a 1 in 3 chance for every formation they still have).
Also the five scrolls in the first game. If you equip all five, your elemental attacks becomes One-Hit Kill attacks that severely damages officers. On a similar note the "Demon" element from the second game, which was changed in Xtreme Legends.
Matzukaze, Keiji's horse, will make you One-Hit Kill anything that your ride over if going at top speed.
In SW1, Okuni's charge attacks (notably charge 2) possess ridiculous amounts of power.
In the second installment, Musashi is hilariously broken for three reasons. Firstly, he has the personal skill Reversal. Whereas other characters can be stunlocked if struck several times in succession, Musashi can just hit the charge button and interrupt the combo to send his attackers-turned-victims flying. Secondly, he has an ability that stuns enemies and gives him free Musou, which means that he has unlimited Limit Breaks at his beck and call. Also, did we mention that he has one of the most devastating Musou attacks in the game?
Tadakatsu Honda is known as this series' Lu Bu, but the Interlude compares him to Zhange Fei, however he is mildly faster than both (probably having above average speed between SW characters) and all his attacks causes absurdly high damage! Not only that but his two Specials allows him to stun enemies and regain 1/2 of musou and to cause contact damage on enemies. His Musou can clean a room in SECONDS.
Germans Love David Hasselhoff: When Koshosho was revealed, the Japanese are really annoyed at her design and her list of manipulated men includes 'Sengoku Musou fans', that were pissed that she made it in with her outrageous design when other more popular choices like Miyoshi Choukei or even Motochika's wife Nana didn't make the cut (and to wit, Pixiv hasn't gotten a fanart about her and it's going to take awhile or none at all for her fanart to appear, while Hayakawa did get her fanart quick enough). Western-wise, she's considered to be utterly fabulous that some are considering to make her their favorites.
MST3K Mantra - Spears in cannons that fire laser beams, ancient Nipponese shoop-da-woops from Ofuda scrolls, ninja with arms straight out of Gumby, European plate mail in 16th century Japan... just turn your brain off before playing. For your own sake.
Sengoku Basara got away with it with more ludicrous examples. Compared to that, the anachronism here isn't half as bad.
Truth in Television on the plate mail part. Armors in the late 16th century Japan was in fact influenced by Western plate armors after things like muskets start to show up. Nobunaga himself was historically a foreign artifact fanatic and had worn quite a few so called "Nanban" style armors in occasions.
No Export for You - It's been announced that Samurai Warriors 3 XL/Z and Chronicles 2nd will not have an international release. Much to the fans' rejoicing, it's also been announced that 4 WILL make it to overseas.
Replacement Scrappy - Despite having her own fanbase, Nene has earned the ire of some fans for replacing Kunoichi (who was removed) in SW2. The fact that they have similar movesets (especially as Nene was never a ninja in real life) doesn't help her case. While Kunoichi does return in SW3, the fact that her role is more centered towards Yukimura (and, to a degree, Kaihime) while Nene is shown to do more ninja activities (including sharing a rivalry/relationship with Hanzo) doesn't put an end to the "Nene shouldn't be a ninja" debates.
The Scrappy - To some, Ii Naotora isn't exactly welcomed due to her meek and Reluctant Warrior personality which reminds them of Daqiao, and made even worse because she's one of the few female daimyo in history (thus they expected a total Badass). And worse further, they fear that her inclusion means they won't be seeing fan-favorite Ii Naomasa (her adopted son, one of Tokugawa's Shi-Tennou nicknamed the Red Devil) anytime soon.
That One Level - In Katana, the second Saika mission with Ina. You have to defeat 15 enemies [including transport units] in 4 minutes (slightly extendable via the Magatama item). The ninjas are invincible when they prepare to teleport out of your sight. Curiously enough, the game actively avoids Luck-Based Mission here and instead hits Guide Dang It. How? Any specific enemy appears ONLY when you enter a certain intersection from a certain direction. Once this is realized, The level becomes more a case of plotting out your exact route through the map so as to get the most amount of ninjas to appear in the shortest amount of time.
Sakon Shima's Dream is a pain even on Easy. Why does it count as if Ieyasu escaped if only one of his doubles (And you KNOW it is a double) does?! Added Hideyoshi, Mitsuhide and Tadakatsu have this strange habit of getting to your main camp.
They pay a little more attention to her history in SW3:XL. Though they still skip on the reason she's famous. Chances are it's to avoid any religious controversy.
In a subtle case of Fridge Brilliance though, one of the interludes in Warriors Orochi 2 (the English version of Maou Sairin) Mitsuhide beckoning that Gracia greet another character, the English VA using a "talking to a little child" voice. Whether or not the VA himself knew it, Mitsuhide was historically Gracia's father.
He probably knew it, considering that she calls him Father several times in the stage directly proceeding that interlude, and his ally quotes to her include calling her "[his] girl". Plus, he seriously got mad when DongZhuo is making advances on Gracia.
Well, there has been a call for adding Hosokawa Tadaoki in the next installment, you know, Gracia's husband, as a playable. If they do that then probably they might go with the wasted plot instead.
KOEI also deliberately removed every references of Hideyoshi's infamous and disastrous Korean Campaign, not just to 'whitewash' Hideyoshi, they probably know that they don't wanna piss the Koreans off.
Unpopular Popular Character - Katsuie's relationship with Oichi (historically, it's rumored that they were engaged to be married before Nobunaga decided that a political alliance with Nagamasa was more profitable) is severely downplayed to the point of it being nearly non-existant in favor of her relationship with Nagamasa. However, if fighting the Battle of Shizugatake (Katsuie vs. Hideyoshi to "succeed" Nobunaga) she is on Katsuie's side.
As a matter of fact, it seems to be a running gag in the series. He uses female motion sets, is voiced by a woman in the Japanese games (and in English as well, starting from the second), and is frequently used to Drop A Bridget OnChivalrous Pervert Saika Magoichi and other such characters.
In Samurai Warriors 2: Empires, Ranmaru is sometimes aware of this, but there's a conversation between Ranmaru and Kanetsugu where somehow Ranmaru is oblivious to his own femininity (even if just in appearance).
Mori Ranmaru: I will put on a disguise and slip into enemy territory!
Naoe Kanetsugu: I would advise against it, Ranmaru. You've failed at playing dress-up once before; remember, when you once attempted to pass as a monk.
Mori Ranmaru: I still don't understand how the enemy spotted me that time.... They said something like, 'there are no girls in the priesthood'. What could that possibly mean?...
In Noh and Oichi's SW2 Gaiden stages, they fight every other female character in the game in order to settle who was the most beautiful woman in the land. One of your opponents is Ranmaru.
The Woobie - Many characters could be considered this depending on what story you are playing through. Ranmaru in SW1 is a good example; everyone he cares about is trying to kill each other.
Nohime: " Ranmaru... did you ever know.. happiness?"
Woolseyism: - In the Japanese version, defeating an enemy general makes the character exclaim "Tekishou, uchitottari!" AKA "Enemy Officer Defeated!". Dynasty Warriors mostly go with direct translation, but Samurai Warriors translates with variations to the point that by the 2nd game, NOBODY ever said exactly "Enemy Officer Defeated!" when they defeat a general.
Now in the 3rd game, each character has two variable "Enemy officer defeated" lines with the first one being the standard "Tekishou uchitottari" and the second one tailored to the character's personality.
What The Hell, Casting Agency? - Your mileage may vary, as it depends on which version you played first; it certainly doesn't help that the roster gets cleaned out with every numeral.
Most seem to agree that Keiji's VA in SW2 was a definite downgrade from his well-loved one in SW1.