Imperial Guard
Company Command Squad
3x Melta, 1x Flamer
Chimera, hull heavy bolter
Veterans
2x Melta 1x Flamer
Chimera, hull heavy bolter
Veterans
2x Plasma, 1x Flamer
Chimera, hull heavy bolter
Hydra, hull heavy bolter
Hydra, hull heavy bolter
500 on the dot
That's 12 Multi-laser shots, 15 Heavy Bolter Shots, and 8 twin-linked Autocannon Shots hammering you from turn 1. Foot slogging infantry aren't going to make it across the board, and there's a enough shots to torrent ranged enemies in cover without difficulty. Light vehicles are going to be blasted apart by turn 2. Heavy vehicles and fast Feel no Pain troops are the only weaknesses. Strategy against both is to spread out. Hydras in corners to get side armor shots against predators and hammerheads. Chimeras stick to cover until they can hit heavy stuff with melta. Against a Land Raider the Command Squad can suicide, because the raider will have almost no support.
Scariest thing would be BA jump packs with a priest, but you're not going to fit more than 20 guys into a list with a HQ and a jump priest. So the Guard again spread out and hammer the jumpers from range until Melta and Plasma can try to finish off a weakened squad.
I don't think there's much this won't roll.
Edit: On an unrelated note; I don't know how the angry face at the top got there, and I can't figure out how to get rid of it.