I wish I had friends who were decent at Gears of War 2. I have one or two friends who I can do well with if we have it on like Casual difficulty, and even then, one of them has this nasty habbit of dying right at the beginning of the wave, making me have to complete the wave on my own.
I do have friends to play Left 4 Dead with, but one in particular thinks it's scary for some bizzare reason. The only "scary" part I recall is the Witch, which is diminished a bit when you realize she's highlighted with a bright red spotlight.
Also, my friends are generally not nearly as good at Guitar Hero as I am, making Co-Op difficult.