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.
YMMV: The Witcher 2: Assassins of Kings
Complete Monster: Bernard Loredo is the thuggish Commandant of Flotsam who runs the town like his own personal fiefdom, running criminal enterprises and instituting racist policies against nonhumans. When Iorveth's men kill some of Loredo's, Loredo sends out his soldiers to incite riots against the innocent, nonhuman residents of Flotsam, leading to butchery and mass murder of nonhumans in the streets. Eventually, Loredo has the Scoia'tael members and their sympathizers rounded up on a prison barge which he plans on sinking instead of delivering to prison. If Geralt sides with Roche and kills Loredo, the Witcher will discover, despite Loredo's hatred of nonhumans, the Commandant imprisoned, beat and raped an elven woman for a year, eventually impregnating her. The woman was so traumatized by the events that immediately after giving birth she killed herself. Should Geralt choose to side with Iorveth and hijack the prison barge, Loredo responds by spitefully trying to burn down a building full of elven women. If Geralt chooses to save the women rather than kill Loredo, Loredo will succeed in turning traitor and selling out Flotsam to the kingdom of Kaedwen.
Game Breaker: The one from the previous game, the Igni Sign had been nerfed, but Aard and Quen (and even Axii to a point) can easily reach this level.
Bombs. You can make a load of them and just chuck them out like candies. Works especially well on bosses, even better if you brought the skill that multiplies the damage dealt by 100%. And the fact they just need two most common alchemy ingredients makes it all easier.
Heck, Igni still counts too, you just have to invest in it. With maxed spell damage enhancements and skills, hammering the sign key to machine gun out fireballs will rapidly drain the health of anything not immune to fire. If your enemy is one of the few which is fireproof, blast em' anyway- a single blast from Igni will force them into a few seconds of flinch animation, dropping their guard.
Golden Ending: While no clear "good ending" is even possible, there are few better choices and their quality of "good" itself can vary. Of course this can also change with the release of Witcher 3. Almost all of them are counter-intuitive.
Saving Triss is always better for the world in the long run than securing any other person, no matter which side was picked. This is the only path leading to reinstitution of Council and Chapter of Mages, thus restoring the balance of powers and securing cooperation between mages and kings, instead of rampant powerplay in style of Philippa's Lodge. Not saving Triss personally leads to pogroms of mages and magnifies the chaos in the North even further, additionally robbing kings of their (often well-meaning and trusted) advisors and high courtiers and sowing distrust among Nordlings. This choice makes much more sense after reading the saga and playing the games - almost all the mess in the whole franchise was caused after the Council and Chapter were disbanded in the wake of Thanedd coup.
Giving Ana´s to Radovid is better than sending her to John Natalis - as Roche points out, better to be a protectorate of Redania than succumb into a civil war and doing so right when Nilfgaard started it's invasion. The civil war could be possible even worse than partiation of Temeria into baronies.
Stomaching what Henselt did and letting him alive means that Kaedwen will hold fast rather than desintegrating like Temeria and Aedirn did. If Kaedwen falls into interregum anarchy, this leaves Redania as the only country in the North, while lands of Kaedwen, Aedirn, Temeria and (unmentioned in the game) Lyria will fall into hands of Nilfgaard without any trouble, thus leading to situation where Redania will fall eventually, stripped of any potential allies and being surrounded by Nilfgaard. If Henselt remains in power, Kaedwen takes Aedirn and Pontar Valley, but the country is still there, with it's ruler in charge.
Most controversial choice requires from player to intentionally weaken Northern Kingdoms and thus shortening the inevetable war with Nilfgaard into a series of mopping operations rather than all-out war.
The deciding factor for most players killing or sparing Henselt is probably whether or not they can stomach the thought of him living after raping Ves and gloating about it right in front of Geralt and Roche.
The above doubles as one for Roche. Henselt just killed all of his men and raped Ves. His purpose through the game was to track down the kingslayer, only to be willing (or for some, successfully) to become one himself.
Depending on the playthrough, Loredo has a few potential moments where he may have crossed it, exactly when depends on the player. The first can be when he arranges for riots and mass murder of innocent nonhumans in Flotsam. The second can be when Geralt sides with Roche and discovers Loredo's kept an elven woman as a Sex Slave for a year. The third can be when Geralt sides with Iorveth and Loredo personally sets fire to a house full of innocent elven women just to spite the Witcher.
The heartbeat sound when you drink a Cat potion. There's a reason that mods on PC that increase potion effect longevity leave Cat alone.
Narm: The fact that Letho seems to talk in an extremely Southern accent seems rather out of place in the setting and makes some of his dialogue hard to take seriously.
Only in English dubb. In original Polish dubb he's voiced by actor associated with playing and voicing die-hard badasses, without any accent, which blends flawlessly into the character.
Stripperiffic: Saskia's armor shows a lot of cleavage over providing protection to her heart and lungs. Potential Fridge Brilliance however, as she doesn't need the protection anyway, given that she's actually a dragon; her ability to heal is epitomised by quickly recovering from impalement at the end of chapter 3. Also, the sexy look could help sway the peasantry to her cause.