You can't take an AoO if you are flatfooted.
So if you try a combat maneuver on someone who is flatfooted (let's say they haven't acted yet at the beginning of combat) they can't get an AoO on you for doing so, right? So if you get the init, you can get a free chance to Bull Rush or Overrun etc, without their attacking you. Seems like they'd also be denied Dex to CMD.
Please correct me if I am wrong about any of these assumptions.
Okay. Now what about a combat maneuver like Overrun? This allows the target to choose to step out of the way. They can't get an AoO, but can they choose to step out of the way if they are flatfooted?
Flat-Footed: A character who has not yet acted during a combat is flat-footed, unable to react normally to the situation. A flat-footed character loses his Dexterity bonus to AC (if any) and cannot make attacks of opportunity.
Yes they can because nothing in the Flat-Footed description (RAW)prevents it. You are surprised and your reflexes are slow (no DEX) but you still can act instinctively to avoid damage etc. Reflexe saves, immediate actions, raise your shield (for the shield AC bonus) etc. are other examples.