i carried a spyderco military, and it always worked. no springs to get sand in, no little buttons to try and find, or get clogged with sand, no finish to wear off, the handle gives grip with nomex gloves on, and the finger hole is big enough to use with nomex gloves as well. plus, its user serviceable. i can take it apart to either clean or repair it whenever i want. its a very basic, lightweight knife, that can sharpen easily, and hold up to a lot of crap. it worked perfect.
The only other really tough pocket knife i took out to the field, was the original sog tomcat. it was the cockiest knife ive ever carried. the spine of that knife was thicker than most fixed blades ive carried. i lost it that field maneuver lol. but it was a dam stout knife.