Rocket Launcher

You don't spend 6 to do 1. Note the designation "Poly Artifact". You lay it out, then later channel as much into the the thing as you can, spraying direct damage as you choose between as may targets as you like, all without the need for a single red mana. Fallen Empire's Aeolipile is regarded as great because it brings direct damage to any color. Same idea here, just on a much larger scale.

Pretty good in a mono blue deck. Put a Power Artifact on this and you have deal X damage divided any way you choose among any number of targets. Yeah, that's good. And of course, if you have a Power Artifact on a Basalt Manolith with this card out, well... game over.

Worst card in Magic? Doubt that. Hello, Ashnod's Altar and various kobolds/ornithopters/squirrels/thallids/whatevers.

This must be the worst card in MTG.

Here is why:
You have to pay 4 colorless to put this artifact into play, keep in mind that this is the same price as for example Icy Manipulator.
Then, you have to pay 2 colorless to give 1 damage.....ONE damage....to a player or creature. Now you've used 6 mana to give 1 damage, and at the end of the turn, the artifact is sacrificed! You can activate the ability as many times as you want, but you have to use 2 more mana to give 1 more damage, wich is a mana cost that's so hilariously high compared to the damage it deals, that it's not worth it. And you have to wait a round for it, cause the artifact has summoning sickness for some strange reason!
Now compare this to Shock.
Rocket Launcher costs 4 colorless, you have to wait 'till next turn, and then you have to use 4 new colorless to give 2 damage.
Shock costs one mountain, it's instant, and deals 2 damage.
Ok, so you need a mountain, but there are lot's of artifacts that give spesific mana when it's tapped, so it's a bigger chance you'll be able to play Shock before being able to use this lousy artifact.

+ It's a bad drawing of one of the turtles shooting a rocket launcher. >_>