Regarding size...
I like a much larger knife. Something with a blade length in the 3" to 3.25" range usually. Above this and the knife gets too heavy to carry in my RFP and, frankly, too scary for the general public so I'm less likely to use it. Below this, and I have trouble getting my XL hands on it and I get frustrated because I use my pocket knife for food pretty much daily and short blades don't reach deep in the peanut butter jar or across fat sandwiches well. Here's a bunch with some commentary...
This is the Opinel #9. Handle is thinned and blade dropped. Easily my most commonly carried combo. (The Micra rides in my LFP with my money clip.).
Opinel #9 Inox Drop Point & Micra by
Pinnah, on Flickr
My Buck 500. This is an older one with micarta scales. My favorite Buck and the second most commonly carried knife.
Buck 500 Duke & Micra by
Pinnah, on Flickr
My Case Sodbuster. This is my 3rd most commonly carried knife.
<no picture... too busy... just imagine it... it's blue and looks just like any other Case Sodbuster that is blue...>
Lastly, the Buck 112. IMO, this is the prettiest production knife ever made. It's a bit thick though and a bit heavy. The other knives get carried more often but it stays in my EDC bowl with the other 3.
Buck 112 by
Pinnah, on Flickr
All of these knives fit my hand well, handle food and wood work well and aren't too big for pocket carry and don't scare people. That's what's in my EDC bowl. The rest of the pictures that follow are knives that stored away. They're either too big for EDC use or too small and frustrating for me.
The Schrade 5OT. A real emotional favorite but too small for my needs. I do carry this whenever life forces me (rarely) into dress slacks. If I could give up food prep, I could deal with this for EDC.
Shrade 5OT by
Pinnah, on Flickr
My most loved and least carried knife.... The Buck 110. Everybody should own one. I don't carry mine often though. Just too big and I can't deal with holster carry. I keep one in my car. I carry this older one hunting. Perhaps they'll make a slim line version some day.
Buck 110 by
Pinnah, on Flickr
The "Pocket Buster", the Schrade 51OT. This is a beast. I carry this occasionally just for grins. This destroys a stack of potatoes. And just holding it in your hand is an experience. What a monster.
Schrade 51OT by
Pinnah, on Flickr