The one that planted the concept of a time-killer game was Desktop Tower Defense! It’s gone away a couple of times, but I’m glad to see that it’s playable again. I spent hours that should have been productive at work playing this game.
Into the realm of iOS, I bounce into new games all the time. My two fall-backs are Hill Climb Racing and Jetpack Joyride. Jetpack falls to the back of the pack faster since I have everything I want in-game, but with Hill Climb the vehicle upgrades get to be so expensive that I haven’t even purchased all of the vehicles yet. I just saw when searching for that image that HCR2 is coming in December!