For me it's three with a probable soon to be fourth.
1. Spyderco - The warranty, combined with the affordability of great EDC knives is awesome. Combine that with almost plenty of combinations of knives and steel and handles, you get a pretty solid company.
2. Cold Steel - JBC already alluded to this but Cold Steel knives are what I would consider working knives. The Tri-Ad lock is stupid strong, I've had zero blade play with my recon 1. And the prices are unbeatable, ex. Recon 1 (S35VN, 4", G-10, Tri-Ad) for 75 bucks on Amazon when I got it.
3. Microtech - Just awesome fit and finish combined with plenty of options. The ultratech is something to behold as is the Socom Elite. My only gripe is the price but tight tolerances cost money.
4. CRK - My grail knife (Large Sebenza 31)t I plan on getting for a graduation gift to myself. The warranty and company speak volumes to CRK's values. I love how they've continued to improve their reputation as well. Again, price is a gripe, especially with the material choices, but my gosh you can't beat that warranty and service (or so I've been told by you guys!).