I knew it.
Yes, it's during the fight to the death between Anakin Skywalker, aka the newly named (though yet to be cooked and cyborged) Darth Vader, and Obi-Wan Kenobi. About partway through the fight, they try to use the Force against each other simultaneously with those gestures. At first, they have a little tug-of-war impasse, before blasting each other away.
Okay, someone else try.
Four minutes? That's ages! What if I get bored? I need a television, a couple of books. Anyone for chess? Bring me knitting.
-The Eighth Doctor, defiant in the face of death, in Doctor Who: The Night of the Doctor