If you want to go really deep, there's the inspire mechanic, the merfolk from Lorwyn/Shadowmoor block, and the untap symbol ('{ Q }' without spaces on Scryfall), e.g.
King Macar, the Gold-Cursed
Pain Seer
Fallowsage
Stonybrook Schoolmaster
Hollowsage
Wake Thrasher
Merrow Reejerey
Order of...