I'll give one of the 50 different answers...

1. 2x Warhounds. Very useful for early activations on turn 1. Surprisingly resilient, fast and deadly against light formations. Also a good shout for suppressing/killing enemy flak.
2. Tacs with Supreme Commander. Not everyone takes a SC but I never leave home home without one.
3. Thunderhawk with either 2x Devs, 2x Assault or one of each. With no terminators you want this for "deep strike" capability, Timing is critical with this group, too early and you will find the enemy counter attack does as much damage as your attack, too late, and you have spent too long with a fair amount of troops not doing anything (so the rest of your army is fighting uphill odds for too long).
4. Whirlwinds + Hunter. I always like to have at least one formation with a template attack. It is a deterent against the enemy bunching up his units too much. If he does the templates punish him, if he spreads out too much to compensate it is easier to find good clipping assaults.
5. Thunderbolts. A cheap formation that can be a lot more deadly than they seem on paper. If you need them for AA then that is their first priority. If they are not needed for AA the ability to strike anywhere on the table is useful, especially for punishing broken formations (where with BMs 1 kill becomes 3).
6 Landspeeders. A unit or two with the scout ability is very useful (I think the scout ability has already been discussed in this thread). With Landspeeders you have a fast unit that can add a lot of firepower in support of an assault.
That would be a solid start IMO.
You could add a large Tac formation for a BTS (with Hunter and Razorbacks).
Some more Land Speeders and or Bikes for a fast engagement style force.
Swap out the wahounds for a Reaver perhaps for a tougher BTS.
Add another Thawk for more air assault ability (with either the regular assault/dev load or a cheap load like bikes).
Add some tanks for more AT firepower (Land Raiders or Predator Annihilators).
And extra points can go on chaplains or librarians (probably in the THawk group).