Hmm. I've never seen a 'slap' by anyone actually make someone go flying.
However, sounds like a fun new project for someone (like, perhaps someone who's returning home soon *smile*) to pick up on.
Possible command names.
"shove", "push"
Turn them into a ragdoll then apply force, perhaps in direction the person performing the action is looking, or if done from console, the direction player, or up, left.
I don't know. Just throwing out ideas built on eggnoggins