Im just using it for everyday tasks. Possibly for self defence. As for blade length something under 4 inches it good.
Here are some of my EDC (every day carry) favorites.
Byrd Meadowlark in G-10 - $25.00 price range
Voted Blade Magazine value of the year. You won't find a nicer made knife in similar materials for that price anywhere, highly recommended. Also see the Cara Cara, which is the same knife with a longer blade and handle.
Spyderco Scorpius - $60 price range
This is one of the really comfortable, awesome cutting ability, slim, easily pocketable knifes that really doesn't get enough attention because it looks funny. One of my favorite mid size EDC designs.
Spyderco Centofante IV - $45 price range
This is a nice, thin, light knife that looks good, and i happen to love the straight (wharnecliffe) blade shape for EDC tasks.
Spyderco Delica - $45.00 price range
This is the no brainer EDC recommendation. Just a time tested and well loved design that works well. Many swear by it. Also available in stainless steel handles, and check out the Endura if you want the same knife, only larger.
Blade Tech Pro Hunter Lite - $45.00 price range
These are just a really good all around design and the price is excellent.
Boker Subcom - $30.00 price range
They are a bit small for some things, but the design is excellent.
Kershaw Leek - $45.00 price range
This is another awesome design that is a favorite EDC for many. It's slim, built well, made in America with excellent warrenty and all that good stuff. It's has an assited opening feature similar to a switchblade, only not illegal.
Kershaw Mini Cyclone - $50.00 price range
Another assited opener, but this one has the option to turn it off, which i think is awesome. Cool design.
The Benchmades you suggested are all great ideas as well, and you should also check out the Griptillian series. If you want to know anyhting specific about any of the knives I posted, just say so. I've owned all of them but the Cyclone, and can tell you more about them.