Gotta say I'm quite surprised by some of these answers.
Never thought I'd hear a bad thing about Spyderco, particularly favorites like the Delica and Tenacious (not personally into those models but I love my Endura and my value Resilience).
Same goes for Benchmades when some have decided they won't buy ANY at all.
A few I saw don't like Buck and the Vantage... I just ordered one hoping to add to my budget user knife category (my favorite category to grow). Hope it's good.
I am not into most of CRKTs offerings but I really like my M-21 although I don't carry it often.
And from the few responses about Case I have to wonder if they've changed over the years? Last one I bought was about 10 years ago and although I don't carry traditional slipjoints often it is one I'll always be glad I bought, looks pretty and a long, thin pair of blades on it.
When my father was growing up, Case was pretty much THE company that combined effective working class blades with aesthetic beauty, so when I was growing up I always thought of Case fondly as a company that produced quality that also looked pretty.
A lot of the knives I still have but don't use much I probably wouldn't buy again just because I try to only buy knives I know I will use, I'm not into collecting just to have it sit around... but most that come to mind are when I was young and first into collecting... Frost, S&W, and the like. I even had a few... M-Techs....
And although I can't really stick up for Gerber... I've had a few Gator folders that have performed very well as budget blades, no complaints at all. Despite the fact that I probably wouldn't buy anything else Gerber (my first knife after I got my first paycheck was an A.R. 3.5) I can't complain about the Gators, perhaps the only model I can really stick up for, which sadly doesn't say much.