Other items I bring are a good back pack, day purse/hippie bag, (nothing screams "rob me I am a tourist" like a big ass fanny pack), a microfibre towel if the accommodations are on the cheap side, and a good assortment of over the counter remedies.
I know what you are thinking... 2 pairs of socks.... really? But I literally live in my Keen Antigua flip flops no matter the terrain unless it is absolutely freezing. They are amazing supportive flip flops (which seems like an oxymoron). See: Keen Flip Flops
Now when we go to northern India which is cold and then all the way south to snorkel I am going to include the super duper light long johns and snorkeling equipment (such a pain to haul but worth it if you are spending a good chunk of time snorkeling. rented stuff is dodgy).