Tinker
 
Fun fact: Tinker was intended as a "fixed", as in more cleanly templated and easy to understand, version of Transmute Artifact from Antiquities. At least, that was how it was envisioned by Mark Rosewater: he also removed the requirement that the caster pay the difference between the cost of the sacrificed artifact and the one being searched for, which made the effect completely broken in both the Urza-era Standard and Vintage. The abundance of zero- and one-mana artifacts in Magic meant that anything, from the biggest, nastiest artifact creature you can think of to game-breaking unique effects, was just three mana away. It turns out Darksteel Colossus and Planar Portal are pretty good when you don't have to pay for them.
 
Constructed: 4/5 (if not banned!)
Casual: 4/5
Limited: 3/5 (I accidentally Phyrexian Colossus)
Multiplayer: 4/5
EDH/Commander: 4/5 (if not banned!)

Today's card of the day is Tinker which is a three mana Blue sorcery that has you sacrifice an artifact to search your library for an artifact and put it into play.  Used with cards like Blightsteel Colossus this is an incredibly powerful threat that wins games at any stage, including the first few turns.  This is banned in most formats for good reason and is one of the strongest theme support cards available in Blue.
 
Constructed: 5.0
Casual: 5.0
Limited: 5.0
Multiplayer: 5.0