Been playing skyrim for a while and it was an interesting game, esp the shouts. Had an idea then that some of these shouts may be possibly made into a mod for L4D2. Below listed are some abilities which i think can apply to L4D2.
For those who didnt play skyrim, the main char in the game has a special ability to shout with force with different types of shouts.
Wuld ... Nah Kest! (Whirlwind Sprint) - Charge forward like the charger in a straight line
Fus. Ro Dah! (Unrelenting Force) - stagger all enemies caught in the blast.
Iiss. Slen Nus! (Ice Form) - an enemy is frozen for a short while. Perhaps make it Tank affected only?
Fo. Krah Diin! (Frost Breath) - enemies caught in the blast are slowed
Yor. Toor Shul! (Fire Breath) - enemies caught in the blast are set on fire
Su. Grah Dun! (Elemental Fury) - faster melee swing speeds or cooldown.
Fiem. Zii Gron! (Become Ethereal) - you cant be attacked and you cant attack.
Reference on the Shouting abilities :
http://elderscrolls.wikia.com/wiki/Dragon_shouts
Hope somebody is interested enough to make a mod of this! The above link has downloadable sound files.