Exodus - My band played with them a couple of years ago and we let them use our equipment. We were all on stage showing them our stuff and just shooting the shit. Really nice guys, especially Tom Hunting, he was standing stage side watching me and came up to me right when we finished to tell me how awesome I was
Keep of Kalessin - Just met them last week at Nile. The singer and bassist went to the merch booth right away and were very cool down to earth guys.
Jeff Loomis - All around nice guy. He showed up to one of my bands shows and I didn't recognize him, but he kept saying hi to me and said "good job *thumbs up*" after our set, very sweet guy.
dammit... there are a ton more I've met but they have all left my mind right now.
I have not met any really dickish bands yet, but one band that I do not like now due to one member is Blackguard. I saw them on their first US tour, very nice guys, thankful for my girlfriend at the time and I for coming out, hung out after the show... totally cool. UNTIL one of them kept flirting with my girlfriend, eventually sending her an email saying how much he loves her and wants to be with her forever... yeah.