There are multiple weapons that have that effect.
all have the same turquoise/orange effect, which you can see in the demonstration videos of those pages.
Finally the Amputator taunt called Medicating Melody
also displays this effect.
If you want to understand which effect it really is, you need to look for the source. The soldier's banners get raised while active and have the special color. Which of the banners is being used can only really be said by looking at the soldier.
The Amputator taunt can easily be identified by the taunting medic. The Quick Fix Über only affects the medic and his current healing target, while the other items affect everybody who is in a certain radius.