Pros:

- Adorable awesomeness. 
- Ghostbusters + L4D = two awesome things in one.
- Tank is a little easier to spot.
- It's the Stay Puft Marshmallow Man... what more do I need to say? 

Cons:

- Only one tiny thing that I wont deduct points for because I'd get hit either way, but it's hard to tell when the tank's swinging his hand at you to throw you and exactly where his arms are. 
-But otherwise NOTHING!

Conclusion:

One tiny little con, that doesn't make much of a difference either way. The fact that it's the Stay Puft Marshmallow Man far outweighs any possible cons! 
Being a Ghostbusters fan, this is definitely an awesome mod! I'm so glad you made this!