This is for Tin Shorts, since he apparently is asking for this kind of thing.
Shiv of Speed - this dagger is made for nefarious no-good-niks who pull knives on people and shiv them.
for S&W and Old-School Clones: You always gain initiative on any round you use this dagger. You may declare you are using the dagger after initiative is rolled, and drop another weapon in favor of it. It strikes twice per round, but must strike the same target twice. For all purposes it is a +2 dagger.
for GURPS: This small knife can be readied automatically on your turn as if Fast-Drawn. It gains you Extra Attack (Multistrike) which must be used for this weapon; both attacks must be against the same target. You strike first in any situation of Partial Surprise, and, if using Speed-based initiative, are considered to have a Speed higher than any other combatant for purposes of determining Initiative. It is Accuracy +2 and Puissance +2, both Power 20.
There, maybe that is useful for you Tim. I thought that up pretty much as I wrote it.