Triangle Wizard is good if the thing you want to do is blow stuff up with spells. Lots of ways of doing it, with a ridiculous amount of class/race/faith combinations available, many of which subtly (or not so subtly) effect the way your spells are cast. Homing spells, split spells, great big flamethrower attached to spells, there's a bit of everything. It's not pretty (spells are, creatures are just letters) and it's a bit slow, terrible interface, but it's quite good for all that. Roguelike, so random, so each playthrough is "different", but real time do there's stuff to do (walk around or kill stuff). But it's mainly different because it takes ages to go through even half of the more interesting combos. You can even play as a hero summoner and watch them all run off and explode each other with poorly thought out spell use (people shouldn't use Fireball or Death Cloud in close quarters, but they do, every time).
Really wish TW got multi-player. That would be hilarious.
Magika also fits into this sort of mould, but better, and it is quite pretty. Plus, multi-player with friendly fire is awesome fun. LOTS of ways to kill stuff, including your own teammates.
Pathos: the Nethack Codex is just like Nethack, but with most of the annoying bits taken out and with a really good interface. So it's quick to play. There's plenty of classes, plenty of tools, crafting, and even multi-player in development under the diagnostic menu (I haven't tried it yet, but MP NH sounds great). Available on PC and mobile, so do stuff on whatever platform you happen to have at the time.