I love Setsuna's "I AM GUNDAM!", because the game even mocks it at one point...you get an email from him that's entitled "Oh, I forgot", and then the message is literally him remembering to tell you that "I AM GUNDAM!'.
My favorite part of Gundam DW is the goofy voice acting and out-of-context quotes, it's great.
And I've never watched the Gundam Wing dub, but honestly, whoever does Treize's voice in Dynasty Warriors is awesome. Treize has the best quotes too, and the new guy does a great job. "Having forgotten the meaning of battle, I can shoot an opponent through the heart without feeling guilt" is my favorite (I don't remember the full quote exactly), even though it's actually taken out of context from the show since he used that line to argue against the Mobile Dolls.
I agree with you about Garrod, though, his voice is pretty obnoxious. The voice they got for Loran, though, is great. I thought it was Debbie Debbyberry (Jimmy Neutron and Zach Bell), but it's apparently some singer named Annika Odegard.