Fire rate from the Ogre and Orc, plus the Orc can pass its splitting projectiles buff. No ricocheting that I've noticed.
The Antagonist makes the vehicle deflect bullets. No homing slag projectiles.
Adaptive shields.. I've only seen it with explosive damage from the barrels of enemy Bandit Technicals, but that visual and audio cue when gaining an elemental resistance can trigger, except there was no change in damage numbers received.
I haven't tested much with the Sandskiff or Fanboat, but the Sandskiff's sawblades can also get the Grog's drunken spread.