I found OMD to be quite an awesome game. Sure, it doesn't do multiplayer (which DD does), but on the flipside, the singleplayer is amazingly good (which is ridiculously hard in DD, since it's geared towards co-op).

What i really like about OMD (other than the silly humor) is that you get a new toy after every level. This COMPELS you to finish up, since you're curious about what you get next time. Auto-ballista in particular had me giggling like a madman. c:

Also, Nightmare mode is cruel and evil.