I suggest -10% Movement speed when active, cuz heavy, and
50% Crit rate chance after every kill for 6 seconds
Maybe all class? This concept is cool IMO since it brings frustration of both sides with a mini challenge.

+ On kill : 5 seconds of crits only on This weapon
+ 100 % of crits on other wearers of This weapon
- 20 % movement speed when deployee
- 30 % slower rate
Only for Scout

omg if this really adds the stats and it gonna be ingame, everyone will fear scouts...

+mini-crits have stun for 3 seconds
-5% speed
-10% swim rate

+Can be used by both scout and heavy
On heavy:
+20% movement speed
-20% damage
On scout:
+20% damage
-20% movement speed

+25% Damage

-15% move speed, when active
-35% swing speed