Sunset from Mather Point on the South Rim. Grand Canyon.
Another trip highly recommended, is visiting the grand canyon national park. This site puts everything into perspective, and the views will blow you away. If possible take off for a week and explore the surrounding areas, you won't regret it.
Mather Point, the rim trail is unreal. Make sure you go around 1-2 hours before sunset, earlier if your up for a linger hike.