Toolcraft Exemplar
 
This is a very subtle encouragement for aggressive decks to go a little slower; to emphasize Affinity-style synergy rather than Boros-style pure speed. The number of cards that do that in various ways mean that it's harder than ever to justify an aggressive deck that lacks a theme or a synergistic element, when you consider the possible payoffs. Aggressive white decks always interact well with artifacts (cf. Puresteel Paladin, etc), and while you might not see a need for the stat boost once you have your Loxodon Warhammers and Bonesplitters on the table, remember that you are still paying only one mana for a creature that would sometimes cost three or four times as much.
 
Constructed: 4/5
Casual: 5/5
Limited: 4/5
Multiplayer: 3/5
EDH/Commander: 3/5

Toolcraft Exemplar (12/9)

In combat, Toolcraft Exemplar is very promising. 3/2 is pretty powerful in the early game, and 3/2 with first strike means a lot of combat decisions end badly for them. And this is all for one mana, and he’s possibly attacking as a 3/2 on turn 2!

The major downside is that he's only a 3/2 during combat, and he demands that you have artifacts around him. Without those, he's really underwhelming, and he's also in an awkward color for wanting to really benefit from artifacts (white tends to be pretty agnostic towards shiny things). He's good if well-supported, but I question if even his efficiency when set-up is enough to get him any play.

Constructed: 3

Casual: 3.5

Limited: 4

Multiplayer: 1.75

Commander: 1.75