Simian Spirit Guide can obviously be used as a target, but thats a pretty tough way to do it
For example, check out this W/R Tokens deck: Creatures (21) 4 Precinct Captain 2 Sunhome Guildmage 2 Ogre Battledriver 2 Purphoros, God of the Forge 4 Soldier of the Pantheon 4 Brimaz, King of Oreskos 3 Eidolon of Countless Battles Planeswalkers (3) Lands (27) Spells (9) We could totally maindeck Revoke Existence, but every reactive card is one less creature to get pumped by Spear of Heliod, Eidolon of Countless Battles, Ogre Battledriver, Purphoros, and Sunhome Guildmage
It will resolve before the spell that caused it to trigger, even if that spell has been countered or otherwise left the stack
8 Minnie Mouse, Musketeer Champion (Enchanted) - $82.40 Set Four, Ursula's Return If you're playing a musketeer deck, Minnie needs to be a part of it
This card only gets better as more otters join in, even if I skip fixing mana for green