Urza, Lord High Artificer As annoying to play against in the 99 as it is from an opponents command zone, Urza, Lord High Artificer is the most popular mono-blue commander for a reason
Fae of Wishes A key part of stuff to do with your almost infinite mana in Omnath, Locus of Creation decks when that was legal in Standard for a microsecond, Fae of Wishes sees the most play these days as a flexible part of Rona, Herald of Invasion combo decks in Pioneer
The loop fuels more plays
Dragonhawk, Fate's Tempest Dragonhawk, Fate's Tempest needs to be in a creature-centric deck to do real work, but it does so much if you have enough 4-power creatures (which is a lovely call back to the ferocious mechanic from this creatures plane of origin)
Anyone who has ever used an MTG card database to build a Commander deck knows that there are a LOT of Magic: The Gathering cards