Thada Adel, Acquisitor : This gal was particularly interesting when thinking about Mishra since there are quite a few commonly played artifacts out there, and if she steals one youve got in your deck, you can play it and then with Mishras ability, go get your own copy
Affinity can equip it to any creature, sacrifice that creature to Arcbound Ravager, and get a +1/+1 counter and two cards
Doctor's companion (You can have two commanders if the other is the Doctor.) Legendary Creature Artifact - Dog Robot Kinnan, Bonder Prodigy Whenever you tap a nonland permanent for mana, add one mana of any type that permanent produced
Theyre some of the most popular mana rocks, and for good reason: theyre efficient, they give you two colors, and they dont cost you any life to use