In League of Legends, once the game is over do players become untargetable? For instance, if an Ashe on the winning team shot an arrow from her own fountain to the other team's fountain before the end of the game, would the arrow still explode if it hit one of the enemy champions after the end of the game?
Abilities like Ashe's or Jinx' ultimate will pass through enemy champions once the game has ended (read: when the Nexus destruction animation is playing).
Basically, any skillshot based abilities will not hit champions anymore and targeted abilities like e.g. Vi's ultimate will finish their animation but will not affect the targeted champion any longer.