Well...
Everybody got so nice and so much detailed suggestions about the scoring system, that it would take millions of fucking days for 1 guy to make it. What about improving the basic score system that wont take too much time.
You should trust the people not put 1 to stats whore boi and the other one to Guy doing duty. We do it too...
How about, every 10 Presi kill or 50 normal kills = 5 shuriken, kunai or Greanade Luncher for 10 min?