I don't honestly think it's fair to trash talk ANY character from Metal Gear, people. Rose DID serve a purpose, as being the way the fake Colonel and Rose led him on later. Plus, Rose played a solid part in Raiden's personal storyline, especially at the end.
And, I'm not disagreeing with the fact that Raiden is an androgynous, whiny twat-monkey, but he could at least jump and cartwheel in a very impressive fashion, even whilst covering his exposed genitalia with one hand. Bet you can't do that, eh?
Oh, and as for most useless character? Hum...going to have to go with Liara from Mass Effect. Quite possibly to most commonly incapacitated and weakest character usable in your party, I found my self wanting to kill her myself, in combat. She put herself directly between your bullets and their intended targets, and her biotic whatnots were complete rubbish. I always just used Wrex and Garrus, possibly the two most badass characters in the game, besides yourself (if you choose to be evil that is).