I use XTEND, which is a mix of BCAAs including glutamine. And there's also glutamine in the protein I use.
I've been playing around with a fat burner for the past couple weeks that contains l-carnitine. There's caffeine and some random herbs/amino acids/alkaloids thrown in as well though, along with CLA in one of the protein powders I use... so I can't really comment on their individual effectiveness, but I certainly don't have any complaints. No negative sides that I've noticed, and I'm usually sensitive to just about everything.