You don’t choose a target for the enters ability. If you choose to sacrifice a creature or Vehicle, a second trigger, called a reflexive trigger, is put on the stack, and you choose a target for that one. Players may respond as normal to this new triggered ability.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.