Somewhere along the line after automated infections are in, it would be cool if long/short blade users could infect people with their filthy, filthy blades.
I imagine it tying in with the ideas from the blood spatter thread ( http://www.sindome.org/bgbb/game-discussion/ideas/blood-splatter-on-weapons-1341/ ) and some of the future features I've heard thrown around about maintaining/cleaning bladed weapons. If you take a dip in the sewers with your butterfly knife out and then stab someone you might give them ebola or something.
It'd probably be balanced out by dirty/unmaintained blades doing less damage.
CHUMMER