Legend of Grimrock from the last HumbleBundle is eating away my time currently.
It's an update of the old grid-based Dungeon Master games, with an editor, so there's lots of (excellent) user content out too...
( Tab Hunter, Wed 23 Jan 2013, 16:28, Reply)

Have you tried FTL?
One of the best indie games i've every played.
It's surpassed Civ5 in amount of time played now.
( Amadeus So long and thanks for all the phish, Wed 23 Jan 2013, 16:57, Reply)

Not my cup of tea, tbh.

( Tab Hunter, Wed 23 Jan 2013, 17:43, Reply)