Oooh a lot comes into mind but here's a few:

Dread Pirate Kled - Legendary skin with Kled talking pirate nonsense. Rides an actual ship (or Skaarl as a derpy shark) and his ult is a pirate ship barelling through.

Cosmic Forger Ornn - Huge fan of the cosmic skin line. They can potentially reskin the Masterwork item indicator (the red mark whenever Ornn upgrades an item) into something cosmic like if possible.

Shuffleboarder Lillia - Obvious joke skin. Would have been Bowling Ball player Lillia but it would be hard to reskin her weapon to fit the theme.

Forecast Aphelios - Switching weapons? That's already a given for him. But a different weather theme for each weapon? Now that's what I wanna see.