I loved wasting time on some tower defense games and action-RPG games.
Here are a few of the latest ones:
- Kingdom Rush (tower defense): http://armorgames.com/play/12141/kingdom-rush
- Last Stand (zombie survival action RPG): http://armorgames.com/play/12009/the...and-union-city
- Cursed Treasure (Tower defense): http://armorgames.com/play/5803/cursed-treasure
- Corporation (Strategy/planning): http://armorgames.com/play/7348/corporation-inc
- Gemcraft (3 games of tower defense): http://armorgames.com/play/10317/gemcraft-labyrinth
Most will occupy an afternoon or 2.