John Connor manages to wipe out Skynet's main base and apparently primary factory in one night and almost by mistake. While at the same time proving that his conspiracy theory was absolutely correct. While saving his teenage father. While resuscitating Marcus. While not dying from a massive chest wound. Just John in general.
How about just screaming, "Do it, you son of a bitch!" and getting his facial lacerations from the T-800's cooling hand?!
He gets a smaller one when he first appears, landing a helicopter on a Terminator and shooting it twice in the head.
The sudden appearance of the T-800, which happens to look exactly like Arnold in 1984. Also notable in that this is the first time in the film that the iconic Terminator theme actually plays.
The opening scene is awesome as well. Not only does it hammer in the fact that the war against the machines has begun, but after seeing a lot of scenes of the future from the previous films where everything is dark and hopeless, as if humanity is fighting a losing war, it's just epic and blood-pumping to see that humanity is able to kick ass and take names.
Teen Kyle Reese and Star, a little girl, taking out a terminator by themselves. And apparently being the only members of the Los Angeles Resistance as well.
Marcus being told that he is a Skynet program designed to infiltrate the resistance. His creator tells him that he will not be the hero of the story and that he cannot save John Connor. Marcus' response? "Watch me."
Then he throws a chair right at the monitor Steve Wilkos-style, leaving it into thousands of bits.