Focus on rarity and long-term appreciation potential
The second ability here, which lets you create a Construct token that scales with your artifacts in play, is solid if a bit hard to commit to in the early game
And there's always one or two fake cards, like, hidden amongst them, which people just have no idea they have
Creature - Rhino Color tag templates(None) Managorger Hydra Trample Whenever a player casts a spell, put a +1/+1 counter on this creature
Mox Ruby is third for Wheel of Fortune, Red Elemental Blast (due to blue being that good when you unleash the ancient weapons) and occasionally a deck of little red men and several variations on doing three damage for one or two mana
Vivi Ornitier Plenty has been written of the design mistake that was Vivi Ornitier