The uber for this is 8 seconds of invulnerability. It heals a standard 24 health per second on target (scales up to 72 if target hasn't been damaged for 15 seconds) A basic strategy to employ is to heal everyone even if there walking to the battle field, as it provides valuable overheal (50% of target's max), which improves the chance on anything from capping a point to pushing the cart (the payload doesn't provide overheal like Medi Guns).

Class Priority for Uber:
Top: Soldiers Demomen Heavys
Mid: Pyros
Low: Scouts Engineers Medics Snipers Spies
There isn't a priority for general healing, as it is good to keep EVERYONE around you overhealed, especially fragile classes such as Scout and Sniper, as it gives them a better chance against classes with more health or firepower, such as Soldier and Heavy.
It isn't recommended to pocket the low tier classes on the priority list, as they don't have the raw firepower that Soldier, Demoman and Heavy do at mid range, and the Uber is better utilised on a class with higher damage output.

This guy right here is where the fastest heals in the game come from. It heals at a standard rate of 36 (+50% that of stock), or 108 health points if damage has been avoided for 15 seconds by your target. On the downsides though, It only gives 25% overheal, in comparison to other Medi Guns which give 50%. A good tactic to employ is to use this in situation where lots of team mates are close, as the faster healing provides a serious buff to your entire team, 50% faster than other Medi Guns.

It's Ubercharge triples the healing rate to 108-324 health per second, which is good if you need to rescue multiple teammates in a pinch.

It also allows you to mimic the movement speed of other faster classes (scouts, booties/eyelander demos, shpeed shpees), which is good for getting to the front lines faster, and allows you to also mimic the explosive jumps of Soldiers and Demomen!

However, this is not reccomended if you are pocketing, as the 25% overheal leaves your heal target slightly squishier, and it's Uber doesn't protect against large bursts of damage.

This thing is sinfully a murder machine came from hitler's factory the vacinator came from hell dont underrestimate it uber whoever if they are a pyro dont bother using the fire resistenace unless used to save yourself

This is not a bad medigun. Healing at the same rate as the stock, but filling Uber 25% faster. Amazing for defense, where you are assaulted by numerous high burst damage enemies, as the guaranteed Critical Hits can annihilate anyone stupid unlucky enough to be in your heal target's sights. On offense, it's not a good idea as it does this is the kritsizer and he does not put a fight for handling he's easy to control he'll ride you to the mvps he is a lovable give the uber to a soldier no pyros and demos maybe a heavy