One of my favorite hikes on Oahu is the hike to Makapu'u Point on the Ka Iwi State Scenic Shoreline.
The park and trailhead are located off of the Kalanianaole Highway (Hwy. 72) at the southeasternmost point of Oahu. From Honolulu, take the H1 freeway east until it becomes Highway 72. Follow the road beyond Hawaii Kai, Hanauma Bay and Sandy Beach Park until you reach the new parking area on the right side of highway.
The hike itself is not difficult and you can easily make a roundtrip in less than two hours. There is little protection from the sun, so be sure to bring a hat, sunscreen and plenty of water. You'll also want to bring a pair of binoculars and your camera.
The hike offers outstanding views of Oahu's southeastern coastline, including Sandy Beach, Koko Head and Koko Crater. At the trail's destination at Makapu'u Head, there are two lookouts with excellent views of the windward coast as well as Manana Island (Rabbit Island) and Kaohikaipu Island (Turtle Island).
You'll also have great views of the red-roofed Makapu‘u Lighthouse built in 1909, and on a clear day the islands of Lana'i and Moloka'i. You're likely to spot humpback whales in season (November-May) and many species of sea-birds.