OK here we go!

New infected
Charger that slams survivors down to the ground until stopped, Spitter that spews acid, and Jockey that jumps on you and controls where you move.
The original special infected are still here with slight differences in appearance.
The tank is more flesh colored and the smoker has more tentacles.
Also in the daylight areas the witch walks around instead of sitting in one spot.

There are now uncommon infected that have talents.
The hazmat zombie is immune to fire because it wears the hazmat suit, mud men which crawl and can cover your screen with mud, clowns(I hate clowns so) that make idle infected follow him and leads them to attack whoever he attacks, riot zombie wearing bullet proof armor that must be shot from behind.

Melee weapons are awesome the chainsaw kill the fastest but runs out of gas.
Melee weapons take up pistol slot.

There is a magnum which has infinite ammo like pistol and is stronger, but can't duel wield it.

There are new weapons like the ak47 and riot gun along with the originals.
There is a grenade launcher that blows s**t up.

New supplies.
Incendiary ammo makes your bullets catch infected on fire, explosive ammo blows them up, ammo packs are portable packs that when used sets out ammo for your team, laser sites increase accuracy, boomer bile is puke in a jar that when thrown at something the horde will attack it instead of you, adrenaline temporarily increases health and makes everything you do faster like run, reload, and heal, and finally the defibrillator that revives dead team mates.

There are new modes like survival, you stay alive as long as you can. There is realism mode which make the game harder like only head shots kill infected and alot more walking witches. And then there's Scavenge which is 4 vs 4 player competition. The survivors need to get 16 tanks of gas and put it in a generator before time runs out. Each tank adds time. The infected of course have to stop them.

This game is AWESOME and I am enjoying it greatly.

Quick note please excuse my crappy typing in this because I spent half an hour typing a really good topic for this but my PC froze and now have to retype everything all sloppy and not as good.