Depends on which beach and what I'm planning to do there.
Sometimes I take my camera gear to photograph the sunrise or sunset. Sometimes I take a small camera so I can take pictures of nearby things of interest even if I can't take pictures of anything distant.
If the beach is likely to have lots of shells I take a bag to gather them.
Aside from that, some combination of sun cream, insect repellant, a water bottle and a hat.