I'd most like to meet any of the Nebulans on the Autobot side, because I'd totally do binary bonding just so I'd never be weak or helpless again. (The 'Con -Masters would likely vaporize me before I could ask to sign up, plus the 'bots would be a bit more forgiving if I didn't turn out to be an ideal soldier.)
Sky-Byte from RiD also seems like a decent guy, with a soft spot for humans, and could provide some insight and poetry. Worth listening to, probably.
I'd least like to meet Tarantulas. because while he's fun to watch while safely on the other side of the TV screen, were I within web's reach, the result would probably be the slowest, most painful death possible with a rather gruesome method of disposal afterwards. Hope I give him indigestion.
Ditto for BW Rampage, though to a ver slightly lesser extent, because his twisted, tortured psyche is truly intriguing and if I'm lucky, the anguish might yield a moment of tantalizing insight before my spine is ripped out and used for dental floss. Not worth it, but if I had to choose between him and Tarantulas and didn't have the option of killing myself first, I'd pick him.
Also, keep me the hell away from Starscream. I have to work with someone like that, and I can't imagine a giant robot version would piss me off any less...