+1 on new JATO. Aren't there some extra Solid Rocket Boosters left over from the Space Shuttle Program?
The NC-130B was the one and only 6-engine Herc (4 T56 turboprops, and 2 extra T56 turbojets to produce bleed air for the boundary layer control system). The BLC system dropped the stall speeds down to the Cessna 172 range, but it was tricky to control because the ailerons lost effectiveness.
Beyond the other variants Clark mentioned, there was the AWACS mod (not sure if the Navy or Coast Guard still flies these), the C-130WB (Wide Body), a three-holer jet version, a lighter 2-engine version, and the Super-STOL Credible Sport I/II. Most people focus on the massive rocket package, but Credible Sport had several other mods like the extended dorsal, double-slotted flaps, and extended-chord ailerons.
For the finest in 1980's technology, look no further than the Lockheed-built C-130 High Technology Test Bed (HTTB). But seriously, the HTTB was badass with a host of STOL, control, propulsion, and landing gear upgrades that should have made their way to the J model. You'll notice a lot of similarities in among HTTB and my list. Unfortunately, HTTB and its crew were lost during engine-out takeoff testing in 1993.