Rakdos Signet

Mobile Garrison

Whenever Mobile Garrison attacks, untap another target artifact or creature you control.
Crew 2 (Tap any number of creatures you control with total power 2 or more: This Vehicle becomes an artifact creature until end of turn.)

Junktroller

Defender
{T}: Put target card from a graveyard on the bottom of its owner's library.

Izzet Signet

Blitz Automaton

Prototype {2}{R} — 3/2 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
Haste

Azorius Signet

Simic Signet

Renegade Freighter

Whenever Renegade Freighter attacks, it gets +1/+1 and gains trample until end of turn.
Crew 2 (Tap any number of creatures you control with total power 2 or more: This Vehicle becomes an artifact creature until end of turn.)

Silent Dart

{4}, {T}, Sacrifice Silent Dart: It deals 3 damage to target creature.

Gate Colossus

This spell costs {1} less to cast for each Gate you control.
This creature can't be blocked by creatures with power 2 or less.
Whenever a Gate you control enters, you may put this card from your graveyard on top of your library.

Thundersteel Colossus

Trample, haste
Crew 2 (Tap any number of creatures you control with total power 2 or more: This Vehicle becomes an artifact creature until end of turn.)

Skitterbeam Battalion

Prototype {3}{R}{R} — 2/2 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
Trample, haste
When Skitterbeam Battalion enters, if you cast it, create two tokens that are copies of it.

Dimir Signet

Gruul Signet

Irontread Crusher

Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.)

Civic Saber

Equipped creature gets +1/+0 for each of its colors.
Equip {1}

Hulking Metamorph

Prototype {2}{U}{U} — 3/3 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
You may have Hulking Metamorph enter as a copy of an artifact or creature you control, except it's an artifact creature in addition to its other types, and its power and toughness are equal to Hulking Metamorph's power and toughness.

Golgari Signet

Rust Goliath

Prototype {3}{G}{G} — 3/5 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
Reach, trample

Sky Skiff

Flying
Crew 1 (Tap any number of creatures you control with total power 1 or more: This Vehicle becomes an artifact creature until end of turn.)

Aradara Express

Menace
Crew 4 (Tap any number of creatures you control with total power 4 or more: This Vehicle becomes an artifact creature until end of turn.)

Selesnya Signet

Sword of the Paruns

As long as equipped creature is tapped, tapped creatures you control get +2/+0.
As long as equipped creature is untapped, untapped creatures you control get +0/+2.
{3}: You may tap or untap equipped creature.
Equip {3}

Boros Signet

Bottled Cloister

At the beginning of each opponent's upkeep, exile all cards from your hand face down.
At the beginning of your upkeep, return all cards you own exiled with Bottled Cloister to your hand, then draw a card.

Brute Suit

Vigilance
Crew 1 (Tap any number of creatures you control with total power 1 or more: This Vehicle becomes an artifact creature until end of turn.)