I own both of these:
Amazon.com: GERBER Survival Guardian Back-Up Md: 05803.: Sports & Outdoors
Amazon.com: Gerber 22-01463 Coyote Brown LMF II Infantry Knife: Home Improvement
Took both of them to Afghanistan and Iraq with me. I personally prefer the back-up. It's big enough to do what you need it to, but small enough to carry easily.