1st - ROTF Depth Charge with new head (look like face plated Energon Prime) 2nd - Legends Class Cybertron Hot Shot (Red Version 2, not Excellion) 3rd - No clue about the body, but the head is from Brave.
the one on top looks like a mix between Movie Soundwave and Depth Charge, the one in the middle is Legends Class Excellion/ Hot Shot, the bottom one is I think Armorhide
The orange one makes me think of the generic background characters who get used to fill out scenes, mostly from G1 or Armada.
I just ordered that Depth Charge KO (or one very similar) from KOtoys (along with a bunch of other stuff). Nightstalker Depthcharge Oversize Remolded Shoulder Guns - Revenge of the Fallen at KOTOYS.COM Actually I hadn't even realized he had a different robot mode head.