Duke’s Waikiki   Duke's, the bar and grill in the Outrigger Waikiki Hotel, could only happen in Hawai'i — it's the kind of place where you can see Diamond Head and Waikiki Beach but still get a bargain buffet breakfast and walk in with sand clinging to your slippers. Named for the late, famed Olympic swimmer, surfer and ambassador of aloha, Duke Kahanamoku, the place is decorated with memorabilia from his storied life. The food isn't fancy — eggs, breakfast meats, breads; sandwiches, burgers and salad bar, surf and turf for dinner — but it's filling and you can pay a lot more for the same elsewhere. The daily brunch buffet, which includes some made-to-order items, goes for $14.95 from 7 to 10:30 a.m.  Outrigger Waikiki Hotel, 2335 Kalakaua Ave. 922-2268. dukeswaikiki.com. 7 a.m.-10 p.m., bar kitchen open midnight daily. Reservations recommended. Valet and self-parking. AX, DS, JCB, MC, VS. No checks. Breakfast and lunch: $. Buffet: $$. Dinner: $$$.