Terraria

I recently bought Terraria on Steam.  I was actually so excited about it that I was going to buy my buddy a copy too.  That's when I noticed that the 4-pack was only 10 dollars more so I bought that and gifted out the other two games.  It's pretty fun.  More variety in the different materials than Minecraft and the fact that there are bosses and unique weapons makes the game more interesting.  Although for the sheer fun of building I'd go with Minecraft because I seem to get more satisfaction out of the 3d buildings than 2d.  Maybe something to do with the feel of depth in addition to up/down and left/right.