Virus

Infect, evolve, repeat: Virus.

Drag'n'drop your virus on red blood cells, but beware of white blood cells and antibiotics. After each level, you may enhance your virus (better reproduction, higher defense, and so on).

Bunker

Defend your, well, bunker in: Bunker.

This point-and-click game takes some time to get any challenging.

Snowball 2007

Another "filler" game: Snowball 2007.

You're a snowball rolling down a mountain. You get bigger over time, and as you do you're able to absorb more and more objects (like people and Yetis...), helping you to get bigger even faster. But the bigger you get, the harder it is to steer, and if you hit an object too tough or large to absorb: Game Over. Your score depends on how big your snowball got prior to the final impact.