hmm ok thanks..anyway how do you make a weapon with 0 damage do knockback?
If it's a hitscan weapon then define your firing function like the others in g_weapon.c, but instead of calling G_Damage call some push function that you defined, or simply VectorAdd( target->client->ps.velocity, your_push_vector, target->client->ps.velocity );
If it's a missile-based weapon then you need to look at G_MissileImpact in g_missile.c and do a similar thing there. Every missile calls that function though, so you need to work out how to distinguish your missile (check on classname or something) and only apply the effect if it matches.