To add a sense of mystery and theatre to a game, let the players come across a strange out-of-place artefact. An alien device in a historical setting. A modern piece of technology in a fantasy setting. A relic from Earth in a science fiction setting where Earth doesn't exist. Maps showing unexplored parts of the world. A crystal skull - which is pretty freaky no matter where it shows up.

For bonus points, have the local NPCs dismiss the item as uninteresting, and be surprised when the PCs obsess over it.

Transcript

Nûwsreader: Attenzione! Attenzione! Zees eez un urzhent broadcast for all biolozhical life forms!
C-3PO: "Attenzione"?
GM: It's space-French.
C-3PO: So space-French is Italian?
R2-D2: "Attention" in French is just "attention".
Nûwsreader: Ze droids from Kamino, do not trust zem!
R2-D2: Why would he broadcast not to trust us?
C-3PO: Because we go around hijacking their ships?
Nûwsreader: Don't let zem perform zeir song! It eez—
[SFX]: krash!
GM: A marble statue drops on the broadcaster.
[SFX]: thud! {it's the Venus de Milo}
Luke: What? That's rather dangerous! Is he dead?
Nûwsreader: Non. It was, 'ow you say? 'armless.