There's no public registry of celebrity console ownership. However:
Confirmed Gamers (Past/Present): Snoop Dogg, Wiz Khalifa, Zac Efron, and others have publicly mentioned Xbox gaming. The 360 was the best-selling console of its generation (84M units), so statistically, many celebrities likely owned one.
Better questions: Which celebrities stream on Xbox? What were the most-played 360 games among influencers?