Fist bump

A fist bump was an action where two people bumped the knuckles on their fists together. Graham O'Brien tried to do so with Ryan Sinclair but the latter kept refusing to do so. (TV: Rosa, The Tsuranga Conundrum) However, he eventually returned the gesture. (TV: The Battle of Ranskoor Av Kolos)

Mickey Smith and the Tenth Doctor occasionally bumped fists. (TV: Doomsday, Journey's End)

A human and a dog once fist bumped, with the former shouting "It's battle time!". (WC: New Adventures Await!)