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.
Best Known for the Fanservice: Jo-Beth Casey and to a lesser extent Venus Starr, to the extent that some don't know that the former is from the Timesplitters series.
Catharsis Factor: Arcade: Amateur League: Nightstick: Dam Cold Out Here. First, fire your flare gun at a snowman. Then listen to the screaming. Repeat.
Epileptic Trees: Anya looks a lot like Jo-Beth Casey. Could the teenage girl she constantly rolls her eyes at actually be her 15x-great-grandmother?
Most Annoying Sound: The Space Flies from TS2, with their incessant buzzing that grows to impossibly loud volume as you get closer to them.
That One Boss: The first battle with Jacob Crow in the tenth level of Future Perfect.
The problem mostly comes from getting the three most obvious weapons and then not knowing where the fourth weak point is. They're two side-mounted missile launchers, but they're not immediately visible.
Mansion in TimeSplitters: Future Perfect was scrappy for three reasons. One, Jo-Beth Casey, who sometimes attacks you due to a glitch. Second, Deer Haunter. Third, the last boss of the level. You know which trope he goes under.
The Hooded Man in Future Perfect. You have to protect your past self from Time Assassins and TimeSplitters until he gets to the base it doesn't get bad until the Splitters show up though.
Something to Crow About. Powerful enemies who can fill you full of plasma in a few seconds, shielded enemies you have to switch quickly to the Electrotool and back to defeat, flying mechs not unlike the "boss" of U-Genius U-Genix, annoying rolling robots, the stage is long, there are two bosses, and the latter of those two bosses is That One Boss.
The Robot Factory in Timesplitters 2 is one. With dozens of robots often teleporting in on you, stronger robots that take a lot of hits to go down and wield the deadliest weapons in the level, turrets and floating mines waiting around corners, and your default weapon's laser being able to bounce back and hit you, this level is frustrating to beat even on Easy difficulty. Good luck getting the Rad Racer cartridge on Hard.....
Seinfeld Is Unfunny: The first game isn't regarded well nowadays due to it's barebones presentation and lacking the features introduced in the sequels.
Video Game Cruelty Potential: Play a Team Death Match as a robot with nothing but flamethrowers and make sure none of your enemies are robots. Just do it.
You've definitely played on the Siberia stage in FP just to block an AI team's base with the jeep.