Master Artificer

{t}: Sacrifice an artifact. If you do, search your
library for an artifact card. If that card's mana
value is less than or equal to the sacrificed
artifact's mana value, put it onto the battlefield.
If it's greater, you may pay {x}, where X is the
difference. If you do, put it onto the battlefield.
If you don't, put it into its owner's graveyard.
Then shuffle.
Gimme a sec. A little bailing wire, duct tape, and
some chewing gum... Voila! Juggernaut!