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: Shadow Complex
Awesome Music: Though the music is fairly infrequent, usually only playing during battles or plot scenes, it succeeds in producing an eerie and suspenseful atmosphere. Especially the title screen music.
Catharsis Factor: Meleeing human soldiers and punting Bomba robots, especially after you get the Omega Armor.
Demonic Spiders: The "Storm Shadow ninjas" are stupidly difficult to target, take a stupidly large amount of damage, and deal even more stupidly large damage.
Game Breaker: Many examples. Most are only relevant at extreme lategame - getting the Fusion Helmet, which requires all of the passcodes, infinite subweapons, which requires you to be level 30/40/50 or to find all the foam/missile/grenade packs...
Nightmare Fuel: After flooding a part of the base, you will have to traverse through it multiple times, especially if you're going for 100% Completion. While you traverse the flooded corridors to tune of a sad piano piece, you hear the complex creaking, and are treated to the sight of the numerous corpses of those you inadvertently killed. Even worse is the realization that the rooms you flooded included the cafeteria, where you just saw dozens of mooks sitting down for lunch, and that many of them may very well have been Punch Clock Villains.
Scrappy Mechanic: The ability to shoot at enemies in the background sometimes means that Jason will fire into walls or aim at background targets first rather than those right in front of him, causing you to either blow your attempts at being stealthy or waste ammo (and time reloading.)