A copy of the Cold Steel Delta Dart, as seen below.
My design is a shorter version made to fit on the print bed of a Makerbot Replicator. The Delta Dart is ribbed for purpose of maintaining grip. Ribless version also available. Hole on back is for a keychain ring or cord. Pictures don't show it well, but blade is triangular.
Print as strong as possible. 100% infil, 2 shells seems to work best. Rafting with external support encouraged.