I would like to try other games like Operation 7 where you can build the whole weapon not with just silencers or clips but the whole body of the gun. I have combat arms, but would like to try more. not like wolf team.
More aboutgames weapon customization
Don't quote me on this but I think borderlands had something like that. At least they touted something like that.
I know it's not the main aspect of the game, but Fallout 3 allows you to construct 7 custom weapons. But, I don't think it's quite to the level you're thinking of though.