Always been a fan of Bates. Their GTX boot is very nice.
I've also worn:
Magnum - I felt they wore out quickly
Galls - Cheaply made, but also cheap on price
Danner - Nice but pricey
I've heard good things about the new Converse tactical. It basically looks like they took a pair of converse athletic shoes, and raised the top up to 8". The word is, they function like a tactical boot, but feel like you're wearing sneakers. I've never tried them personally.