Suppose I am attacking a Falcon that has a C-3P0 equipped. Because of some ability, the Falcon's agility has been reduced to 0 for this attack.

In this case, since the Falcon won't roll any agility dice, can C-3P0 still be used? If it can, how does it work? Seems rather odd that my opponent can just guess 0, roll 0 dice, and get a free evade.

C3PO can only be used if you get to roll 1 or more dice.

"Once per round, before you roll 1 or more defense dice..."

C3-PO cannot be used in the example you mention.

Edit: NEEN'jahd...

Kind of throught i strange he came with the Corvette since it almost cant be used with it but how eles could they have released him into the game

Yeah wedge and ships with outmanouver make 3PO cry about the odds.

Kind of throught i strange he came with the Corvette since it almost cant be used with it but how eles could they have released him into the game

If you shoot at a corvette at Range 3 or more, it'll get defense dice and hence C3P0 could be used. It's not really meant for use with the corvette, though, as you note.