If you guys haven’t done it, play Left 4 Dead with thirdperson turned on. It gives you a real sense of immersion that you don’t get through just playing in first person.
Easy tip: Open up your console (turn it on in your advanced key settings) and type:
bind j thirdpersonshoulder
Pressing J will now activate third person for you automatically! (you can replace J with any key) Although word of advice, it doesn’t work on versus.