I've been thinking of adding a "headshot" only mode to All4Dead but you beat me to it!
You might want to add an additional FF mode which mirrors damage taken. So if I shoot someone I take 100% of the damage. Reason I suggest it is I think someone requested it a while back so it might be popular.
Quote:
l4d_damage_ff
0: Friendly fire does no damage.
1: Friendly fire is the same as normal
2: The attacker takes the damage
3: The damage is split between attacker and victim