Quake 4: Completely unable to find any health, armor, or ammo to prepare for any upcoming fights that you just
know you'll be taking damage in. Doesn't help that even the weaker enemies can kill you by themselves and they keep tossing those juggernaut motherfuckers that throw lightning around and have a bigass spike for an arm. Takes like 3 clips to kill those bastards and you can't even find any ammo to fight them with. And like I mentioned you WILL get hit and loose a lot of health per hit, so you're going to have one hell of a time trying to find health and armor packs that are going to be crucial to your survival.
Mass Effect 3 (Multiplayer): Your team won't stick together when you're fighting reapers on Gold, and because of that, you each get gang-raped by a pack of banshees and brutes.
Borderlands 2: Some prick jumps in your game and hoovers up all of the guns from bosses/treasure chests and never even bothers to revive you or help in firefights. Rule of the Game; play with friends only.
XCOM: Enemy Unknown: My magic sniper (with Squad Sight) who can shoot aliens between the eyes, through 4 different sets of walls suddenly won't be able to spot any targets when the rest of my team has eyes on the enemy. That, or my
entire team would be completely unable to land a shot on a Sectopod, when they each had a 75-97% fucking chance of hitting. Then the damn thing kills 2 of my higher ranking men in the following turn.
Guess this goes to show that the
Murphy's Laws of XCOM isn't just some whiney bullshit. It's distubingly (and hilariously) true.