Blocking the plasma pistol is actually very hard at first, but also very cool.
All you need are plasma pistols and a duel weilding weapon.  You need two people for this trick.

1. First have someone charge up a plasma pistol.
2. Get two duel weilding weapons.
3. Weild them.
4. Have that person shoot at you with the plasma pistol.
   
5. Now melee when the charged shot gets really close to you (pretend that you are hitting the plasma shot).
   

TADA!!!  You might not get it on your first try, but when you get it, you feel powerful...

If you can't see the movie below, click here.