Team Fortress 2 and its insistance to crash.
Underhell (Source mod) and its insistance to randomly bug the fuck out and crash, despite it working fluently hours before.
Pokemon Emerald (now that I'm replaying it) and its insistance to... do fucking everything. Miss an attack, enemy has a sliver of health left, you getting poisoned/paralyzed despite the low chance of it happening, randomass critical hits, wild Pokemon not letting you run away (especially fucking Arena Trap, where you have to KO or catch the Pokemon), Wild Pokemon who won't be caught despite your powerful Ultra Ball being thrown, random Rival battles, enemy Pokemon carrying Berries, Gym Leaders who use Full Heals/Hyper Potions on their strongest Pokemon after you chiseled its health down, fucking Confusion status, enemies with Sand-Attack who drop your accuracy to one successful attack out of seven, your frontmost Pokemon (of course) being at a disadvantage to the Wild Pokemon/Trainer you run into, Repels doing jack shit, useless HMs (Flash and Rock Smash especially)...
But I love the game >.>