For Challenge # 023.

Nicely general. It'll work a bit like Mana Flare in that several decks will just get a bit of extra mana from it (from Signets, mana stones, mana Myr etc).

Equip is somewhat amusing. Doubling it (without changing targets) won't do much in most cases, but is great with Surestrike Trident and friends (er, if you have a way to untap the creature as well).

Should this allow changing targets?

My first thought would be to expect a symmetrical Thought Reflection here (in the blue slot).

Unless it's "tap to equip" then equipment won't usually get doubled anyway.

It's a fun one - as you say; more unbalanced than manaflare because; well, everyone runs lands but most don't run half as many artifacts. I can see sideboarding 15 though, whilst this is in the environment.

Also, more difficult to abuse, since, while you may have an artifact heavy deck, only half the permanents in play will be artifacts. In a Mana Flare deck, you don't need other permanents... just land is fine.

I have no idea why I didn't come up with Thought Reflection, but this one seems closer to Mana Flare in theme - doubling tapped things - so I probably would have chosen to go with this anyway.

Changing targets makes sense. Added that.

Accidently wrote "You" instead of "That player" as the person who changes targets. Forking all your opponents activations ftw.

That would be a bit good for the cost; but a yummy effect.