In my opinion, the Ritter Griptillian is a functional upgrade because of its steel and edge geometry. Despite sharing the same handle as the standard Grip, it's a completely different beast IMO, and one of the greatest functional EDC folders ever made!
http://www.knifeworks.com/dougritterrskmk1stonewashedm390bladeknifeworksexclusive.aspx
http://www.knifeworks.com/dougritterminirskmk1stonewashedm390bladeknifeworksexclusive.aspx
It uses M390 steel, and M390 is friggin awesome. Despite being reasonably easy to sharpen and having reasonably good toughness, it holds an edge insanely well, and really shines in cutting abrasive materials and holding an extremely thin edge. For every one time you touch up the M390 Ritter Grip blade, you might have to touch up the 154CM Mini Grip blade 5-10+ times. Unlike most stainless knife steels, it doesn't rapidly lose the scary sharp after just light initial use. The Ritter has also been made in M2 and CPM-M4 high-speed steel, CPM-S30V premium stainless steel, and (a very limited few) ELMAX...all of these are outstanding steels.
For a production knife that costs under 150 bucks, the Ritter Grip's edge geometry has become legendary, developing the reputation of being a survival tool that can handle a wide range of tasks. It requires less physical force to achieve the same cutting outcome, helps hold the edge longer, provides considerable tip & edge toughness, and makes sharpening easier. It slices well enough to perform the tasks where a hollow ground blade's performance attributes are desirable, and yet it can perform tougher tasks where a saber ground blade's performance attributes are desirable.
Many people add aluminum, steel, titanium, brass, G10, or carbon fiber handles/bodies to their Grips (this is most popular among Ritter owners.)
The Spyderco Delica and Endura are another affordable knife line that I absolutely love. Like the Griptillian, there are different blade and steel options. The best overall blade option in my opinion is the FFG or Full Flat Grind. Like the flat grind on the Ritter, the FFG also performs very well with a wide range of tasks. The ultimate steel experience IMO is Super Blue. Like M390, it is an edge holder with very good toughness for what it is, but it is much easier to sharpen, seems to have even better chip resistance, and corrodes very easily.
ZT (owned by Kershaw) also has some really neat models, generally makes knives with outstanding geometry, often uses exceptional steels, and has pioneered several interesting designs in the past 10 year (for example, they developed a ball-bearing system that works with the pivot design to radically reduce wear, maintenance.) They are generally priced higher than Benchmade and Spyderco's entry models, and IMO they are probably the most consistent large production Maker when it comes to consistency and fit & finish. Their limited edition/semi-prod models regularly defy what one would expect from a mass maker, with a quality that is insane. I am digging the 0450 (a modified production version of the 0452cf, both with design similarities to the original semi-prod 0454.
https://zt.kaiusaltd.com/knives
If you are looking for the ultimate folding knife experience of semi-production folders, then a Chris Reeve Sebenza is the golden standard that all other folding knives are compared to.
