Jack's helmet is totally an artifact. It grants nigh-invulnerability. Downsides? It only fails when it's dramatic for it to do so, but when it is a moment of high tension, it will fail, guaranteed.

Max has made a few technological ones. They're called Warblers, and they're freaking awesome.

Erik's coat never gets lost, or damaged, and the wearer can come up with moments of genius (that may well make other artifacts), but you become highly vulnerable to suggestion.

Alfred's suit never needs ironing, and is better than body armour, but you have to speak in an upper class English accent all the time, or it looses it's effect.