Cons:

10 seconds to get a new syringe
-20% attack rate
On miss: Poisons you until you get a health pack

Pros:

On Backstab: Poisons the enemy for 10 seconds and does 20 damage every second and slows the enemy by 10%
On Facestab: Does 10 damage and slows the enemy by 5%

on backstab 20 damage a sec. till enemy dies
+100 damage a sec if the victim is healed by any source
victim gives medic disease if being heald
loose diguise when all victims are dead
loose weopen for 10 secs after five hits including non back stabs

• On backstab: You get cloaked instantly for 3 seconds, can shoot weapons (including melee) during that time
  
• Cannot use cloak for 5 seconds after that period

the mercy killer
level 40 Non-mercy Injector

+ On backstab : Bleeds on target ( - 60 Damage Per Second) but the Victim cannot attack and walks slowly until death

- 32% Damage Penalty
- 15 Seconds to get a new syringe

On kill: become Übercharged for 2 seconds
On hit: enemy can not be healed for 10 seconds
On hit: wearer can not be healed for 10 seconds
50% slower firing speed

The Mercy Killer
level 1-100 epi-pen (ha-ha)
+Removes debuffs (being on fire, bleeding, etc) from allies on hit
+Backstabbing poisons the target, hurting it by 10% of its base health per second
-Backstabs don't kill
-Poison can be removed by medics, medkits and spies with this weapon
-50% damage (that tiny needle ain't gunna really hurt, y'know?)

(-)On kill or use: 10 second recharge
(-) Does not instantly kill
(-)-25% damage
(+)Target takes damage and dies within 5 seconds if not healed
(+)Mouse2: Inject yourself, taking 50 damage, but gaining a speed boost for 5 seconds

Tell me what you think, mates.

i don't like the "non instakill" idea.......i think it will broke the spy concept, and make the knife underpowered

Pros:

On backstab, gains 25% of "Toxin" meter
When activating Toxin, creates an area of effect where enemies cannot be healed by dispensers or Medics for a short period of time.

Cons:

50% damage penalty (it's a needle. it's not going to do much.)

Originally posted by tf2 Heavy, Pootis| trade.tf:

Originally posted by MrFlaptastic:

(-)On kill or use: 10 second recharge
(-) Does not instantly kill
(-)-25% damage
(+)Target takes damage and dies within 5 seconds if not healed
(+)Mouse2: Inject yourself, taking 50 damage, but gaining a speed boost for 5 seconds

Tell me what you think, mates.

Can stop being unorginal and make an other idea dont steal my idea
be orginal. https://youtu.be/Uouxz5fTPHk?t=5s

Mate, you are reverse-copying my ideas before I even post them, even with the video [ecks-dee].
https://youtu.be/Uouxz5fTPHk?t=5s

I think a backstab would be an insta kill BUT it should do a backstab animation longer than any knives, like you gotta uncap something or yadda yadda yadda bla bla bla, something like that...

Welp, It's either this or an instakill, so I dont think it's OP

hmm i'm thinking of

Pros:
On backstab: 6 seconds of dizzyness and 3 seconds of blindness
+5 percent heath back (not saying this a upgrade of PBPP)

Cons:
-15 percent firing speed
Not instant kill
-8 percent heath

idk if this is good or not

Originally posted by MrFlaptastic:

Originally posted by tf2 Heavy, Pootis| trade.tf:

Can stop being unorginal and make an other idea dont steal my idea
be orginal. https://youtu.be/Uouxz5fTPHk?t=5s

Mate, you are reverse-copying my ideas before I even post them, even with the video [ecks-dee].
https://youtu.be/Uouxz5fTPHk?t=5s

That's not how it works.

Originally posted by SilverWind:

Originally posted by MrFlaptastic:

Mate, you are reverse-copying my ideas before I even post them, even with the video [ecks-dee].
https://youtu.be/Uouxz5fTPHk?t=5s

That's not how it works.

How do you know that's not how it works?