When you're playing an MMO on a laggy connection, then stop playing and instantly think "Oh God, NOW my connection starts working!" or you continue to see the lag for several minutes. (It's happened both ways for me!)
Also, Evergrace related, you see something you can't identify, attempt to draw your katana, then realize using nail thrust would take too much palmira.
When putting on heavy clothes, you think "My defense must have went up."
You've been playing too much SSBB when you see a bat and wonder how far/fast you can launch someone with it.
You've been playing Resident Evil 4 too much when you see a bird's nest in a tree and say "OH! Look! I wonder what will come down if I shoot it." while reaching for a handgun before you realize you're saying it aloud.
In my experience, I know I've played too much Black when I see a car or other form of machinery, I begin wondering how many rifle bullets will cause it to detonate.
I swear I have sooo many more,, but that's all I can think of.