I carry a Kershaw Groove. Opens smooth, no flicking necessary. One twitch of the finger and it just glides open, no springs. Advertised in MN when I bought it at like 3.89" which was under the 4" limit. Grips very well and transition to ice pick is just as comfortable. The finger grooves give good grip plus decent texture on the plastic grip panels. It's a little heavy if you ask me but the edge has a nice flow to it that aids in slicing.
http://www.kershawknives.com/product...&brand=kershaw
It's either that or my Gerber Evo Jr. which has a small ~3" blade.
Hunting I carry a Cold Steel Black Rock Hunter and a Bushman. The BRH is slow to open but is a no frills balisong-like knife that went clean through the ribs of the two deer it was used to field dress. Honed right back up afterward.