There are a lot of different options and preferences out there, but for the most part, I think that you’ll find the Charlie’s Slide Pro Capo and the Bradley capo will typically come out on top. I have both and they are both fantastic.
+1 for Charlie's/Bradley. The Charlie's gives marginally better tone than the Bradley, but, for me, the Bradley's more comfortable and compact. Probably just a matter of habit, and I'm sure I'll get used to the Charlie's in time.
I have tried everything, but the Charlie’s and the Bradley have the best tone for sure. The Bradley is a little quicker to install and more comfortable to work around but I mostly use the Charlie’s because it gets much tighter and stays in place better.
I just got a Lapro Squareneck capo from ebay. I'd never heard of it and just kind of stumbled onto it. It's basically a small block of wood that wedges between the fret board and the strings. On the fret board side it's padded and on the top it has basically a fret that the strings rest against and another thin piece of wood locked down across the strings with a set screw like any other capo. It fits a bit too tight so I'm going to have to shave it down a tad, and it's kind of bulky to work with, but it gives my tricone a really, really nice ring. I can't say I'll use it all the time because of the bulk factor, but it sure does sound nice!