iDime334,571 Locked 02 Jul 2011
Maybe, at the end of the game, you have only 9/10 weapon.
The easiest way to find the last weapon is:
Free Play
Battle Race
Pipeline Sprint
When the race start you have to park on the "?" symbol and press Y until it gives the weapon you miss
Achievment unlocked
p.s: sorry for my english, i'm italian.