My favorite: When Sentinel answers Optimus's command for a battle and he uses his Cybertronian sword to scale himself down the building, sending lots of debris to fall onto the street.

 

Blowing a hole in Ironhide.

 

Fending off both Optimus Prime and the other Autobots at the same time. It's easy to see where Optimus learnt his badass skills from.

 

On Cybertron we were gawds! And here... they call us machines.

 

Killing Ironhide.
Ripping out a piece of Megatron's fucking head.
Kicking Optimus' ass.

 

'Seal off the city'

(and also the following events)

 

Never seen that...

 

"What your planets needs are more playgrounds."

 

Awww, that was a beautiful scene. I wish they'd had it in the film....

 

I hate to say it, but the scene in which he killed Ironhide

 

The scene at the mountains with Optimus Prime and the Matrix (wish i knew where it was shot at).

The scene at the Lincoln Memorial.

The order to seal off the city.

"It's OUR world now!"

And of course the Highlander scene with Optimus Prime, and Megatron.

 

Getting his ass kicked by Megatron, man Megatron just made Sentinel look like a rag doll. Followed by, "Nooooo Optimus!!!" It was a great scene, he was practically trying to surrender. Trying to convince Optimus not to kill him, because he knew he was done for. Finally ending with, "You didn't betray me, you betrayed yourself."

 

The part where he betrayed the Autobots and went apeshit on the NEST soldiers.

 

"I hereby discharge you from duty."

 

Sentinel Prime: [to Mearing] I will overlook your condescending tone, if you heed the gravity of mine. The Decepticons must never know the space bridge is here. For in their hands, it would mean the end of your world.

I love that scene...It's like a slap in the face to Mearing to tell her be quiet!

 

When he Bitchslaps Megatron for trying to upstage him while his evil plans are unfolding.

 

every scene he was is in....he was just pure badass lol.

 

him beating the crap out of optimus and the autobots all at once barely taking damage

 

Pretty much every scene, thanks to Nimoy's voicing him to perfection. No line or scene was wasted with him, and his lines deserve to be quoted in the future of Transformers as the lines from the '86 movie are.

"I will overlook your condescending tone..."

"I hereby discharge you from duty." - A great "twist" on "Such heroic nonsense" considering he's killing Ironhide of all people.

"So lost you are, Optimus. On Cybertron, we were gods... and here, they call us machines."

"It is time for the slaves of Earth to recognize their masters... seal off the city."

And of course the final fight where Sentinel throws Optimus, the Autobots, and NEST's collective asses around like rag dolls. Truly a one-man army.

 

Honestly I didn't like him so his most "epic" scene for me was when it finally hits him that he's not gonna win and he starts begging Optimus not to kill him.