Every time there is a major Steam sale, there is one game which I end up with which becomes the star of the show.
In the previous sales, it had been Beat Hazard Ultra, with a twist of the-then newly free Team Fortress 2.
In the holiday sale that ended a few weeks ago, the star ended up being a game called Dungeon Defenders.
And the thing is, I didn't end up buying the main game. Someone I know won a copy as part of the contest, but since they already had it, they gave it to me.
Then I bought everything else including DLC that is yet to be released, and I've put about 60 hours into it already.
The basic jist of the game is it combines tower defense with third person action RPGs in a world that is cel-shaded and cartoonish with a light fantasy story.
It is designed for 4-player co-op play, but it is also very approachable for solo play, and I've done a bit of both during my time with the game. There are some challenges which you need help on based on the logistics, so it is always better to play with the little help from your friends.
There are basically 4 different classes to build a character from: the Squire, who is your traditional knight-type character; the Apprentice, who is your basic mage; the Monk, who builds a lot of support towers and such; and the Huntress, who lays traps and uses crossbows and guns (and there is DLC which allows you to build the characters from the opposite side of the gender divide as well), and their abilities and towers complement each other. Take for instance, the monk has a tower which slows enemies down. When you pair that with the magical elemental towers of the Apprentice, it means that enemies are exposed to damaging projectiles for much longer.
It is a game that is simple from the outset, but which has a lot of depth, and is well worth investing time in, because I have one character almost at the top of the heap levelwise, but there is still a lot more stuff to get and more challenges to attack.
The game is currently available for the PC, PS3 and 360, though the PC version has a lot more DLC available (and is available worldwide, unlike the console versions which I've heard haven't been released in Europe or Australia yet).