I've never seen them done much on EBG, but sweeps maybe. Some would debate their usefulness, but you specifically asked about niche techniques...
They sound badass.
Hybrid picking with pick and fingers combined, like country guitar players does. Pick with a pick and pop- slap with the rest of your fingers. I've heard only one to pull this off with aplomb. Old southern fusion stalwarts Dixie Dregs bassist Andy West is the only one I've seen do hybrid picking on bass...Song "Night Of The Living Dregs" starts at 27:49 hybrid bass solo halfway in...
Modern version of that