Oh, this is hard... My gut instinct is to say the Moby d**k in Space anime. But it was atleast to bad you could laugh at it and enjoy it that way. I mean, the pirates went to a space disco, got in a bar fight, and then went to get ice cream. It was pretty damn hysterical.
So I'll say Divergence Eve. It looked fun and like a fanservicey space show... but it turned out to be super boring and the plot wasn't even worth following along with. It really sucked. Which is sad, because like I said, it really LOOKED like a fun series.