I have two.
Multitask (Engineer Melee) If you hit any building, all your buildings will upgrade/repair/replenish ammo (for sentries) at the same time. Ex: If you hit a level 3 dispenser that has low health, your level 1 sentry with low ammo will be replenished, and your level 2 teleporters will upgrade, while your dispenser is repaired, all at the same time.
and
Krankheit (Medic Medigun) If functions like the Kritzkrieg when healing but has a new function of infecting enemies, just like TFC. Only a medic on the enemy team can heal any infected players. Krankheit means Disease in German. If you are infected, a green toxic symbol will appear above your health cross and the corners of your screen will have a green hue.