A wreck of a starship that provides a new branch of the tech tree (if it branches) else it provides a new tech.
An unstable rift in space that does not lead to node-space but can be studied for a slight research bonus for a few turns before it collapses.
An automated starship construction facility that produces at twice the production rate of your best constructor. For a turn or two before it breaks irreparably.
Artefacts should be giving a SMALL bonus.
like +10% to ship movement or something like that.
These are all small-scale things that do not qualify as Artefacts. That's not to say they might not appear in the game, mind you, just that they're not the sort of thing I want.
Let me make this clear: Artefacts are meant
to have a significant impact
on how the game plays out. They are big. They are potentially gamebreaking if you can complete the necessary research to learn - at the very least - how to use them, and what they do. Ideally, they can help break gridlock scenarios, and provide powerful reasons for factions to go to war with one another... even if the function of an artefact is unknown. Or they can be a considerable encouragement to stay on somebody's good side.
These are not
toys, these are the surviving remnants of a massively advanced race that lived in this layer of the lanespace grid, but died out uncountable millenia ago, or otherwise moved on/left this area of space somehow.
That said, they all vary in usefulness, and not all of them need to be star-killing superweapons, or even weapons at all.