M4A1
Level 10....Rifle?
+500% damage bonus
+500% damage bonus
Crits on headshot
+5 more clip
-25% reload speed
No random critical hits

Revengineer
Shotgun for Engineer (Uses Frontier Justice as a base, no custom model)
+100% damage bonus
+50% faster move speed on wearer
-99% bullet spread (Bullets go in one singular formation)
+500% more bullets in one shot
On Kill: Target user's respawn time is increased to 20 seconds
-99% max primary ammo on wearer (1 ammo)
No random critical hits
-94% clip size (1 clip)
-85% slower reload time
-15 max health on wearer
Disables Secondary
Disables PDA
It's the perfect shotgun to get rid of that most annoying guy on the opposing team. It comes at a cost, though.