Right now, I only have a humble little TUSA mini-bcd knife, that I scored cheap on ebay. It's a sharp, cool little blade, and I'm happy with it.
But the one I miss was a little SeaQuest BC knife that i had back in the 90's. I loved that cheap little knife, it was a favorite piece of gear, that went everywhere with me, for years. The best thing about it was the simple, solid, nearly unbreakable sheath (unlike the thin, brittle TUSA sheath), that held the blade very firmly, without any fragile, complicated, gimmicky locking mechanisms, that are so typical now. You just popped it into place, then yanked it back out. You could drive over that sheath (and knife) with a truck.
It was never the sharpest knife in the drawer (pardon the pun), but 99% of the use it saw was just banging on my tank.
I'd love to find another one someday, if only for nostalgia's sake. This is what they looked like (from an old classified ad I just found on-line).