Reckless Fireweaver

Whenever an artifact you control enters, Reckless Fireweaver deals 1 damage to each opponent.

Roxanne, Starfall Savant

Whenever Roxanne, Starfall Savant enters or attacks, create a tapped colorless artifact token named Meteorite with "When Meteorite enters, it deals 2 damage to any target" and "{T}: Add one mana of any color."
Whenever you tap an artifact token for mana, add one mana of any type that artifact token produced.

Sarinth Greatwurm

Trample
Whenever a land enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")

Rootcast Apprenticeship

Choose three. You may choose the same mode more than once.
• Put two +1/+1 counters on target creature.
• Create a token that's a copy of target token you control.
• Target player creates a 1/1 green Squirrel creature token.
• Target opponent sacrifices a nontoken artifact.