Torbjorn, Trusty Mechanic

When Torbjorn enters the battlefield, search
your library for up to one artifact card, reveal
it, put it into your hand, then shuffle.
{3}{u}{r}, {t}: Create Torbjorns Turret, a
colorless artifact token with "Whenever a
creature attacks you or a planeswalker you
control, Torbjorns Turret deals that creature's
controller 2 damage."