I love “Physics” games, where you have to set up a sequence of events to do a task. I found a little cracker over the holidays, Vampire Physics, you have to convert all the humans to vampires while at the same time making sure that they don’t get killed by all the normal things.
What make the game great is the built in level editor, where you can create your own levels for other users to play. Great fun and it keeps the game fresher for longer.