I'm looking for advice on what kind of figs to compliment him, or particular figs that work well with him, general advice on using him is welcome as well.

I only know what I gathered from the unit section, so this is all theory.

In 300, graviton looks like he would need to be played as a keep away style OMA. Sidestep + friendly version TK lets you place anyone away from you. His range is good, his attack is good enough.

Maybe someone else has actually used him, but that's the impression I get.

He's to low damage to really dish it out. His incap ability with damage is awesome

I played him on a 400 point A.I.M. team with two IIM Dreadnought #006 and two IH A.I.M. Renegade Agents #017. The agents would take turns using Barrier while standing next to Graviton, protecting him until an enemy was in range. The Dreadnoughts could be used as tie up or to boost Graviton/Agents with their Hydra TA. Note they are giants so they can stand behind a friendly Hydra fig and usually see over them, allowing their TA to work. It is a good team but map choice is relevant. On a map like The Warehouse, very close quarters, no long distance ranged attacks, this team will lose. But on most maps it will be great. Also there is 7 points left over for whatever.

In Modern format, I'd try him with Fitz and Simmons from main set NFAoS, and get the Hoverbots outwitting, enhancing, empowering, healing, and the SHIELD TA from when the scientists are adjacent to Gravitron. It's not for a really competitive scene, but might be fun to try. You'd have 5 points for your favorite ID card or something like Terragin Crystals if you wanted.