I used iCab (the Mac port of CAB) for a few years in the early '00s since it had a very good balance of features and resource usage. It's still around but it's been rewritten to use WebKit so there's not really much point to it anymore.
I was using OmniWeb for a while, but basically the same thing happened to it ;)
OmniWeb was great! Loved the vertical tabs. I wish Safari supported them. My screen is far wider than it is tall and vertical scrolling is a natural movement, darn it!