Tezzeret

I often think that if planeswalkers had been made into cards during the Mirrodin block, Jace might have been replaced by Tezzeret.

Tezzeret the Seeker aka "Good Tezzy"

The +1 and -5 on this are pretty decent, allowing you to reuse tapable artifacts and turn artifacts (even lands) into powerful creatures. However, the thing that really makes this card powerful is its -X. "But what could it possibly look for?" I hear being cried out. Well, here's just a short list: Ashnod's Altar, Crucible of Worlds, Extraplanar Lens, Master Transmuter, Myr Galvanizer, any artifact on the battlefield, Staff of Domination, Sword of [insert name here], Unwinding Clock, Whispersilk Cloak, and of course, Reflecting Mirror. In short, not much. Now, it does cost 5, but have a look at the long list of mono-blue artifact tutors. There's only 1 other tutor that doesn't require sacking another artifact: Fabricate, so a reusable tutor in blue is well worth the 5 mana.

Pros: Good all-around abilities
Cons: Only works in an artifact deck
Rating: 4/5

Tezzeret, Agent of Bolas aka "Evil Tezzy"
Again, another artifact-focused cards. The +1 of Peer Through Depths but for artifacts is good because it allows you to dig through your deck to find the right artifact for the job. The -1 lets you hit someone hard with a Welding Jar or something similar. The -4 is pretty spectacular given that you can feasibly have an all-artifact deck and this can hurt a lot (think something like 7-12 damage). This card is 2 colours, but with the Mana Myr, artifact decks usually are not wanting for colour fixing.

Pros: Good all-around abilities
Cons: Only works in an artifact deck
Rating: 4/5