Seemed like so much fun, I created an account so I can complain too!
Coverhugging in 1st person - The Killzone 2 single player is awful. (although by this point I'm pretty sick of first-person shooters. I still like 3rd person though.)
Overcomplicated squad controls in non-RTS/turn-based strategy games. Anyone played Freedom Fighters on PS2? That had squad control almost nailed as far as I'm concerned - a simple 3-button system, with all the controls you need (barring 'hold fire' for when I want to sneak).
When you're an unkillable lord of death, but dealing out said death is not fun.
Stat-heavy games that don't explain what all the stats mean. (Final Fantasy are bad offenders here) This is becoming less of an issue with wikis becoming official documentation, but it used to really bug me.
Single player only RPGs with easily achievable level caps (as in, can be reached playing the main campaign, doing all side quests, little unecessary grinding) - you've let me become an unkillable badass by this point already, any further progression won't make me functionally any more powerful, just give me more toys (by which I mean, fuck you KOTOR, lightbroomhandles won't make me forgive you this one).
Also, anything by bioware where they continue to show me they really liked the combat system system for neverwinter nights (KOTOR and DA:O).
Anything that's been obviously ported from PC to console and done badly (like in DA:O where it's cleary designed so you can have the crapload of hotkeys available on a computer, then restricting me to 6 shortcut commands. Coupled with the fact that that type of combat is only really fun on a computer, where target choice is quick and easy).
Any game that ruins things previous titles in the series worked so hard to set up - like Fallout 3 getting the Fallout atmosphere all wrong and bringing in a fresh batch super mutants for some reason. Or Mercenaries 2 by introducing some silly revenge motive opposed to the plot being: you are a mercenary, go kick ass (and also the game being rubbish).
And finally, anything that is really buggy (if it freezes all the time, I find it no fun).
Oh, also any PC game with above pants computer specs, My EEE just cannot handle it...