Terraria

Yes, yes, Terraria is a lot like Minecraft, what with the building, and the monsters at night, and the Poké and the man and the guy comes out and he oh BOH BAW BAW BOH.  Cosby impression aside, Terraria is more about fighting monsters and purifying the world of corruption than it necessarily is about building fortresses and other impractically ornate landmarks.

One thing that's a huge letdown is that there's no simple building mode.  You can't shut off creeps, goblin invasions, or just give yourself whatever equipment in a sandbox mode.  The 2-dimensional building style is not as impressive as Minecraft's 3D world, although the Terraria creators try to compensate by including fluff items to place in rooms and requiring more specific objects to build things (such as a loom to make cloth).

That said, it does have adventure game elements where Minecraft doesn't; health and magic can be improved.  There are also guns, a welcome addition in a game with several flying enemies, along with other weapon varieties such as lances, boomerangs, and the Tron lightdisc.  Perhaps most fun of all is the inclusion of a hookshot-like weapon and flying abilities.  No minecart shenanigans, sadly.  You can also customized your avatar, but frankly I didn't care much for most of the options, particularly the hair styles.

Connecting in multi-player is irritating.  I don't mind connecting via IP, but I shouldn't need an application like Hamachi to just be able to connect to other players.  The chat line is also limited to a single line, which is bothersome when you need to explain things that take more than a terse sentence.

That said, playing with friends is still a lot of fun.  I got hazed by my online group, via my murder the moment I joined the server.  After calling them assholes, we proceeded to build forts.

One of my buddies then decked me out with hacked gear: Wings, the Hamdrax drill, the Megashark, and Excalibur. Suddenly everything died in a one or two hits, and I could demolish the terrain at high speed.  This was awesome, since my starting equipment took 20 swings to kill even the lowliest jelly monster and 15 seconds to cut trees down. Yes, those starting times were unrealistic to begin with, shut up.  It's still boring and tedious.  I went out and downloaded the inventory hacker on my own, giving myself 10,000 dynamite sticks and other equipment, like armor and the grappling hook.

I then proceeded to blow up the world, one dynamite stick at a time.  It was entertaining to watch all the dirt blocks fall progressively further downward.  This is also a very good way to mine ore quickly, although if you're going to hack your inventory to get the dynamite, you might as well just hack in building materials too (because I like to push laziness to the EXTREME).  Although I quickly lost interest in this destructive activity, I have heard tales of people draining the ocean into hell.

All in all, a nice, cheaper version of Minecraft with a clearer sense of goals (for now, considering the way Minecraft updates are going) that will appeal to suckers for 2D styled games.