Here are the ones I have enjoyed using the most so far:
* Death Company
5x Death Company Marine/jump packs, 3x power sword, power fist, infernus pistol
I put them in Stormraven (extra armor, twin linked lascannon, twin linked multi-melta) and run them straight at the enemy. Note that they typically have a Death Company dreadnaught armed with Blood Talons along for the ride. They will kill just about anything they charge but the Death Company does not last long when the opponent then focus fires upon them. It's fun to scare the crap out of my opponents with this unit.
5x assault terminator/4x pair of lightning claws & thunderhammer/stormshield
This combined unit can either ride in an LRC (extra armor & pintle mounted multi-melta) or a Stormraven (see above configuration). They also do amazing things in close combat but the advantage of this unit is they can weather a lot of enemy shooting. I played an IG army the second mission of the Ard Boyz preliminary round and they took out a 30 man blob of guardsmen in two rounds of close combat then blew up some tanks. I use the stormshield to absorb lascannons and save Corbulo's reroll for this save. They soaked up two squads of veterans blasting at them with plasmaguns before assaulting the tanks and I only lost two of the lightning claw termies.
* Assault Marines
Sanguinary Priest/power sword & infernus pistol
9x assault Marine/meltagun, thunderhammer & stormshield
I have been running this unit either with jump packs (add one more assault Marine with a flamer) or take a landraider (extra armor) as a dedicated transport. This unit has been doing suprisingly well and it's probably my favorite of the three. It really doesn't hurt when they decide to suffer from the Red Thirst & become fearless. The thunderhammer is really great at tackling big nasties like lash princes. I plan on adding a Chaplain for the jump infantry version.
I also want to experiment with a squad of Vanguard veterans (jump packs):
Sergeant - thunderhammer & stormshield, meltabombs
4x Veteran - 4x lightning claw & stormshield, meltabombs
Expensive but probably the most durable due to all the shields. I would run them with a Priest and stick them in a Stormraven as well.