Usually a Pina Colada.    
-flashlight
-Am Ex (good tip from the other thread)  It's tempting to leave your wallet in the cabin.  I am rethinking that.
- multi-tool. 
- Real shoes/surf shoes.  I never wear flip-flops or open shoes as a general rule.
- I think I could get by without the iPhone.  But if I have pocket space...
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Gary