I know you said you aren't going to, but if grenades were to be implemented, I could imagine something similar to the Holy Handgrenade, but it would only knock down the opponent rather than kill him. Also, it would have a drastically smaller throwing distance, blast/effect radius, and deal little to no damage.
P.S. I have absolutely no clue what modders can manipulate in regards to weapon stats so pardon me if this isn't possible.