Which weapons provide the ripe-watermelon head explosion animation?

I was showing off the game to my brother the other day and I whipped out the sniper rifle and sorta hurt someone. After hyping it up a bit, it was unimpressive to say the least.

Well, I reloaded, switched back to my usual rifle and splatter ensued for an appreciative audience.

Which weapons give the head splatter/headless corpse effect or is it a function of the amount of damage delivered? (or something else altogether?)

Most weapons will get the animation, but some will actually not show it.

Any sniper rifle, Carnifex, Phalanx, Claymore, Graal, Saber, Paladin, Eviscerator, and Wraith. Those have the highest chances of doing so.