Your question is bound to spark quite a debate, but I bought myself a Gerber LMF II last year and have been very pleased with it. There are scores of reviews for it online that can help you learn a bit about this great knife.

I carry a Gerber Prodigy Survival Knife anytime I go backpacking. It's a great knife. I've used it for everything, and it hasn't let me down. For an "all in one" survival knife, I would go with anything that's made of strong steel and has a full tang. The Gerber LMF is a good choice.