Making goldenaxe single player.
COD4 and the amount of grenades online (x3 +1 for martyrdom + sonic boom) and these guys just spawn, throw their nades in the air, run in and die, and repeat.
Getting spawn killed.
Games that are too easy, and increasing the difficulty only increases enemy bullet damage and toughness, while leaving them as retarded and non-aggresive as they were on normal. So the game on hard isn't hard, it just takes more time, which is boring.
Backtracking to extend the games playtime. DMC was annoying for this.