I'd say Randy Couture versus Tim Sylvia, one of Royce's earlier fights, the Rampage slam, a JDS fight, and an Anderson Silva fight.
You think Rampage vs Arona is one to show? Maybe if he wants to show some highlight finishes. You can find some sweet HL reels that are amazing. If you want to go that way I'll pass along some epic HLs. Lombard, Shogun, Wand, Erik Silva, Fedor and plenty others have some great ones. Or if you want to go with submissions you can look up Aoki, Gracie, Nog and others. You can show them some wars like Chandler-Alvarez, Hendo-Shogun, Bonnar-Griffin, Chuck-Wand and others. Just depends on what you want to show them.