Gta sa underground is an awesome mod and a work in progress still made by a lot of fantastic people: http://gtaforums.com/topic/776561-wipbetasa-gta-underground-mod-discussion/.
One of the things i loved was the gang wars and the ported weapons of the various games. But my thing is that i loved going into the vanilla data files to edit all of them, and i said to myself why not with Underground?
This mod makes weapons all different and realistic, changed ammo, to some the position and to others the accuracy, making them all different and giving a reason to choose one over another, because they all felt like the same to me.
I would suggest to download the cheat menu mod to lower your weapon skills, trust me it's really funny to level up.
-All ammo have been changed, to some ranges and accuracy, to others the position.
-The normal pistol is held with one hand, compensate the damage it does.
-The equalizer is now in the sniper slot, and for a reason, trust me.
-The skorpion doesn't akimbo when reaching the hitman level, because is now in the pistol slot.
-The silenced colt from VC can be held with one hand, and at hitman akimbed.. It's brutal.
-Scaling levels will make CJ feel more confortable and so mount bigger magazines to guns.
-Mp5k can be akimbed at hitman level.
It takes a lot of them to kill you, but it takes a lot of ammo to kill them.
Lemme know if you think something is off, or if a weapon is unbalanced and all this.