Depends on the beach. I wear Keen H2's all summer, but they are terrible on a beach with small pebbles. More open sandals like Teva's are easier to get the rocks out without removing them. I would go with Teva's for consistent loose dry sand too.
Wet packed sand is easy--- better than most trails, or city sidewalks for that matter, and you could wear just about anything. The tide level and distribution of materials will determine what you are walking on. A PNW beach might have hard packed sand at low tide, or scattered exposed reefs with barnacles and seaweed. At high tide you might find yourself on loose dry sand, loose pebbles (terrible stuff) or picking your way around driftwood. Some headlands require climbing steep banks at high tide and you want all the traction possible. I usually just wear what I used for the trail to the beach: low top shoes in summer and mid-highs in wet/muddy conditions.
If you use aluminum trekking poles, rinse them with fresh water often. They can pit like crazy when salt water beach hiking. If you have some old beaters, take those. Carbon rules :)
I just noticed the original date on this thread :)