Overall there aren't alot of endings that i really like, but these are the ones that sucked imo but its nothing unless a second season will air and fix it just like code geass did (so far..)
-elfen lied: we don't know what happens with the characters
-tenjou tenge: enough said by other people..
-air gear: wow he can jump over a croud, sooo what's next?
-angel sanctuary: the mc was going to save his sister cuz she was dead or something, the end.. :s
-sola: wtf, everybody dies except the lamest character (imo) of the show
Dunno about elfen lied and sola, but all of these animes continue in the manga so that sometimes explains the open endings..
