The scene in the church. In the trailer, last only a few minutes, but just to see three of the biggest 80s action stars in the same scene = Crowning Moment of Awesome.
The best moment is the threat Mr. Church makes to Barney Ross - where he warns Ross not to run off with his money, saying that his people will come after their people. Ross, being Ross, looks utterly bored by the threat.
Mr. Church is himself a walking moment of awesome. He shares a room with both Trench and Ross, and still comes off as the most dangerous man in the room. Ross and Trench even seem to be aware of it.
At the end of Ross & Christmas' recce of the island, Ross jumps for the seaplane as it's leaving the dock - he misses, but catches the edge of the hatch, and drags himself inside. And then, as they're leaving, pissed off at everything, they decide to turn around and give the army a taste of their own medicine. Christmas climbs out from the nose hatch, hits a switch, and unloads with the .50 caliber machineguns as Ross brings the seaplane in for a strafing run. And once the strafing run is finished, Ross dumps jet fuel on top of the dock, as Christmas fires a flare gun into the fuel/air mist. The dock blows up. Then they leave.
Also a meta Moment of Awesome for Stallone, who saw a worker climb out of the hatch of the seaplane the day of filming, and came up with that sequence on the spot.
Lee Christmas vs the Jerk Jock posse - no contest.
"Next time I'll deflate all your balls, friend".
The end of the car chase between Ross and newly-turncoat Gunnar. Wham and BAM.
The preceding hand to hand fight between Yin and Gunnar is also very, very awesome, with both men making maximum use of their body types and the environment.
If it's not the point in the Cold Open when the Expendables manage to get the drop on pirates in their own ship, floating in the sea someplace, it's the point at the end when they plant bombs all over the general's palace with impossible coordination and timing. They're not just about Stuff Blowing Up. These guys know their shit.
Hale Caesar's Big Damn Heroes moment, saving the rest of the crew with his AA-12 in the palace tunnels.
The scene with the entire team running into the yard guns blazing in true action hero fashion.
Ross convincing Hale to throw a mortar shell at Munroe's helicopter, using a handgun to blow it up. And it WORKS.
Lee and Yin's finisher on the Brit.
The final fight between Toll Road and Payne, which ends with Toll kicking Payne into an oil fire to kill him.