Yeah, there's a few hundred achievements (!) which exist for a combination of fun and to unlock the alternate weapons. (If you don't get the achievements, you'

Yeah, there's a few hundred achievements (!) which exist for a combination of fun and to unlock the alternate weapons. (If you don't get the achievements, you'll gradually get the weapons anyway via random "drops" when you die and/or crafting, trading, or (now) RMT.)