That's what hangs of my PFD...

http://www.altrec.com/gerber/river-shorty-knife

Gerber Shorty double edge, doesnt rust, easy to deploy and to attach to my vest. Can be carried upside down. Not much of a camp knife (basic functions but no choping) but because of the double edge I can cut from any angle. It was cheap on ebay and I half expected to loose it or break it but after 4 years it is still going strong.