I was outraged while playing Deus Ex: Human Revolution to be subjected to a terrible bug. During a shoot-out I was pinned down by automatic fire emerging from a blank wall. Obviously there was an enemy soldier behind the wall shooting straight through it; were it was another player I would’ve assumed malicious use of a cheat, but as it was just the AI I gave it the benefit of the doubt. I was all set to make a post starting “Dear Sir, why oh why oh why oh why etc.”, but couldn’t let go of the right mouse button or I would’ve stopped hunkering down in cover and been shot.
On the off chance, I loosed off a few bursts of my own towards where the bullets were coming from, and was slightly surprised to see blood splatters, then the body of a solder materialise from thin air as his cloaking device failed. It wasn’t a bug at all, it was an invisibility suit; I wish the game had warned me, though that might’ve slightly reduced its effectiveness.
I should probably be thankful that the tactical decision of the stealthy enemy was to stand completely still in one place shooting at the boxes I was hiding behind (and equally thankful that those boxes, like all boxes in cover-based shooters, were conveniently packed with concrete, iron plates, kevlar and other composite armours capable of withstanding any projectiles short of an artillery barrage), as if he’d tried something as crazy as “walking around the boxes (while completely undetectable)” I would’ve been in trouble.