Quake 4, as Doom 3, keeps all it's variables in Def files. Reading through these, I've pulled out what I think are the interesting numbers:

Gauntlet
Damage 50
Knockback 50

Machinegun
Damage 7
Knockback 7
Damage_team 5 (I'm guessing this is the MG damage in Team dm)
Knockback_team 5
FireRate .1

Machinegun (zoomed)
Damage 10
Knockback 10
Damage_team 7
Knockback_team 10

Shotgun
Hitscans 11 (I believe this is number of pellets)
Damage 10 (per pellet)
Knockback 10
FireRate 1

Grenade
Damage 100
Knockback 100
FireRate 0.8
Projectile Speed 700
Fuse 2.5

Grenade (Splash)
Damage 100
Radius 150

Hyperblaster
Damage 14
Knockback 14
FireRate 0.08
Projectile Speed 1800

Hyperblaster (splash)
Damage 10
Knockback 10
Radius 35

Lightning Gun
Damage 8
Knockback 8
FireRate 0.05
Range 768 (Q3a value)

Nailgun
Damage 30
Knockback 30
FireRate .16
Projectile Speed 1200

Nailgun Splash
Damage 30
Radius 75
Knockback 30

Rocket Launcher
Damage 100
Knockback 100
FireRate 0.8
Projectile Speed 900

Rocket Launcher Splash
Knockback 100
Damage 100
Radius 120

Railgun
Damage 100
FireRate 1.5


It's possible that I've misinterpretted some things, they aren't all that self explanatory, but I think the numbers look about right.