This is a mod that I wrote a while ago and has been flying around in some servers.
It makes all spectators (including dead players) into visible (random) colored puff clouds.

You can alter following values from MutVisibleSpecsX.ini (or from in-game settings):
ZapDamage=20 - The zap damage spectators can deal.
SpectatorModel=1 - Model type (0 = clouds, 1 = UFO's).
ZapProjSpeed=1000.000000 - Zap projectile speed.
LaserRefireRate=1.000000 - Zap refire rate as spectator.
ZapTime=1.000000 - How long (in seconds) zeds stay zapped.
bAllowFireLaser=True - Allow spectators fire zap lasers.
bLaserZapEnemy=True - Zap projectiles zaps enemies like ZED gun.
ZapHealDamage=2 - While spectating a player, heal this much hitpoints per fire (0 = disabled).