Just base the stats off the holy water from Castlevania.

~while active:
+instantly remove cloak and cannot recloak(3 sec)
+on hit took 25% targets health
-cannot kill enemey below 30% health
~on hit highlight targets

stats
-slows enemy down and reduces their damage against u or any teamates
-extinguishing you're self will grant you 6 seconds of regeration(4+ hp per second)

Slayer's Sacrament:

Fully heals allies on weapon radius as well as removing Fire, Jarate and Mad Milk effects
Enemies will be marked for death for 15 seconds
Enemies will recive damage equivalent to what they do to your allies for 15 seconds
Enemy Pyros will die instantly (optional)
On self-hit: wearer will recieve invencibility for 10 seconds

On self-hit: wearer will be unable to attack for 15 seconds
Friendly Pyros will also die instantly (optional)

small splash area
all foes hit burn with holy fire for X seconds dealing Y damage per second
spies, pryro and demos take double damage and are feared
cannot harm healing medics
reloads from supply cabinet only.

My stats,I don't like this coz "Holy",but whatever.
+Primary Fire to drink,taking 2 seconds to complete but heal 125 health over 3 seconds,any unhealed health will be converted to overheal.
-Cannot attack during drinking period
________________________________________________________________________________
+Secondary Fire to throw the Slayer's Sacrament
+20% of damage dealt to coated enemies is converted to health,any unhealed health is converted to overheal.
+Allies and yourself are "cleansed",removing all debuffs except for bleeding.
-Allies and yourself are wet when used on.
________________________________________________________________________________

hotdog

Or combine it with a Vampire setup for the Spy and build in a minigame like Scout Alien against pyro. That could be really awesome, and just give it jarate stats with an extra on vampire spys. Make the Sniper a Vampire Hunter.

Affected enemy, receives minicrits from all sources.

Instantly decloaks and undisguises spies, preventing them from cloaking or disguising for the duration.

removes buffs applied to enemy and prevents any from being added during duration, doesn't stop ubers. (Demomen temporarily lose their heads bonuses, soldiers cannot toot their horns, players cannot be affected by said horns, scouts are unable to benefit from their cola, heavies lose the buffs from their food.) Opposite is also true, cleasing teamates from negative effects and can gregariously harm Merasmus, the Horseman, and other hellish entities.

Ammo count 3.

Does refill on their own or from dispensers, need medium medkit.

+Insta kills people if it crits
-No random critical hits

perfect

heals friendly players

on friendly hit :
extinguish fire and give 20% damage resistance for 10 second

on enemy hit :
turn taken damage into mini crit (but effect shorter 30% then normal jaratee)

pros:

. when thrown on dead players it can revive them

. extinguishes players that are on fire

. when reviving dead players it will heal the player by 35 health points

. revived players will gain a 25% speed boost for 5 seconds

cons:

. revived players will only have half health

. players cannot be revived twice

. - 25% over-heal from medics

. health packs will give you less health

+Marks enemies for death
+15% splash radius
-Very long charge time

+) On Hit: Ignite the enemy for 'everburn', a flame which cannot be extinguished by water or airblast (but any other means will, such as health packs) and can even ignite enemy Pyros!

+) On Miss: Create a pillar of tall, lingering flame that damage enemies for regular afterburn (pillar lasts approx. 4 seconds)

-) 30 second recharge time, 10 seconds more than Jarate...

+) ...which can be decreased by 20% (4 seconds) by "cleansing" an ally, removing all of their debuffs (charge does not decrease when used on yourself)

-) 50% splash radius