The Punisher

Listed in order of gained points, from least to most.

1) Grenades (less than 100, per grenade regardless of the number of kills)
2) Shooting (100 or less)
3) Interrogation/torture + kill with torture (200 for torture) - this is usually accidental as some torture methods are more difficult to control
4) Quick Kill (200 or less)
5) Melee weapons (250 or less, single use) - useful for cases where you have to use Quick Kill
6) Thrown dagger in Punisher Mode (255 with no point degradation)
7) Interrogation/torture + Quick kill (200 or less for torture 100 or less for quick kill)
8) Special kill or special torture on mob with info (usually 500 or more, one use per location)

Point gain dwindles as you repeat the same action (especially with the same weapon), so you may eventually need to switch down on this list, but the point gains reset for each section or level so it isn't so very permanent.

You gain no points for enemies killed by other enemies, so although you can use living shields, it isn't point efficient and poor accuracy from enemies can kill them too even if you aren't holding them as a shield.