Infectionator is simply awesome. You play as some kind of mad scientist who has the ability to spread a zombie-virus in some town and watch it and all the people become tasty treats to your new zombie army.
Dying people drop money (wut.) which you can pick up (how?) and buy upgrades for (from whom??) your virus with.
The game itself does not require great graphics or sounds, the retro look fits it well and the "bloop bleep" 16-bit-music creates a great retro-feeling about it.
But despite these things, infectionator is really recommendable and quite a bit of fun if you want to procrastinate studying like me.