The Phlogistiblaster. Airblast the ground to shoot yourself into the air. No primary fire. Airblasts are 150% stronger. Airblasting enemies charges up your meter, when full, use primary fire to do a single airblast that is 250% stronger.
But it has the same decals as the rocket jumper and sticky jumper, which do no damage and are usually just used for goofing around with friendlies or on trade servers.
The Friendly Fire
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-75% airblast cost
+25% repressurization rate
+25% push-force on airblast
Extinguishing teammates restores 50 health