Both Buzzwole and Rillaboom commonly run Drain Punch on their sets, and for good reason. Buzzwole gets STAB on it, and when paired with Bulk Up, it becomes a powerful threat. Rillaboom often runs Swords Dance and a Life Orb, which allows Drain Punch to hit even harder. While Rillaboom occasionally opts for Superpower for immediate power, Drain Punch is usually the more reliable option. Similarly, Buzzwole may use Close Combat in some sets, but Drain Punch is generally preferred for its healing and longevity.
Buzzwole (Smogon)
Rillaboom (Smogon)
Hope I helped!