Kershaw seems to own the Bang-for-Buck market if you're talking under $25 (Half-Ton, G10 Hawk, Chill, etc.). CRKT makes some good knives in that price-range (the McGinnis Tuition is one of my favorite knives ever and it was around $15).
At $25-$50, I'd say Spyderco or Byrd are on top of the most-value there. Kershaw makes some good knives in that price-range, but at that point, the Spyderco Delica is top-notch and their Value-line models and pretty much any of the lock-back Byrd knives are a very good deal.
Benchmade's Harley Davidson, Lone Wolf, and HK line don't seem to do much for me personally - but a lot of folks seem to love them.
At ~$100 (for me) it's hands down - the Spyderco Paramilitary-2.