The The Secret Armory of General Knoxx Add-on for Borderlands has 9 achievements worth 235 gamerscore.
Complete all missions in Secret Armory
Pay for a worthless tour of the world's largest bullet
Kill each of the loot midgets
Destroy the Lance Depot
Destroy a Lancer while in a Racer
Rescue Athena
Build the New Car: Monster
Reach Level 61
Kill Crawmerax the Invincible