Go to Leonard's Bakery (Malasadas) and Rainbow Drive-In (Loco Moco). Near each other, loved the food and deserts at both.

Climb Mt. Olomana (but don't almost kill yourself like me)

Diamond Head lookout is fairly easy and worth it.

Lanikai Beach is a must see (Obama's live nearby)

Punahou school is where Obama went. Nice school to walk through.

Nu'Uanu Pali Lookout


that's all I remember for now.