Orks… despite the begrudgings of many, I think they are actually pretty solid in 7th edition, especially if you take into account the Ghazkull Supplement and the trend of other codices in recent months. I also think that the new Ork book allows/encourages fluffy builds (i.e. Green Tide lists, Trukk lists etc,) which are still competitive, which is a big plus.
-Big Mek with Mega Armor and appropriate shooty weapons
-Max Squad of Flash Gitz
-Battlewagon with Deff Roller (Big Mek and Flash Gitz ride in this)
Now, since Mega Armor confers Slow and Purposeful (which applies to the whole unit and makes them count as having not moved) and since the Git Finders on the Flash Gitz increase their BS to 3 if they haven’t moved, the entire Flash Gitz squad should be able to ride forward in the Battlewagon turn 1 and shoot out to max range and with BS3. Now, 10 Flash Gitz put out 30 shots, of which 15 should hit with BS3. Of these, against a normal MEQ opponent, S5 Snazz Guns means that they should inflict about 10 wounds. Now, depending on the random roll for AP, if they roll 1,2, or 3, then that is an entire squad of Marines that just got vaped in a single round of shooting.
If they roll AP4 or worse, then only about 3-4 MEQs dies after armor saves, but you still use Flash Gitz firepower against less well-armored opponents and inflict quite a lot of damage. For example, against a typical Guardsman Equivelant unit (GEQ), Flash Gitz have 30 shots, 15 hits on average, 12-13 wounds and, unless they roll a 6 for AP, that’s 12-13 dead Guardsmen (or Guants, or Cultists, or Guardians, or DE Warriors, etc.etc.). Throw in the Big Mek shooting for additional damage and the Battlewagon’s firepower and you can basically take out a squad a turn.