Miscellaneous: Even if you have a decent base tan the intense Sun on Crete can burn you in no time at all if you don't use sunblock. And if you wait to buy it until you get to Crete the incredibly high prices for it will make you regret not bringing your own. Fortunately we brought plenty, so we did not have to buy any there. Make sure you apply it first thing in the morning because you can easily burn just sitting in your chair at breakfast or driving around with your windows down.
Camping/Beach/Outdoor Gear: The Sun in the Greek Islands is extremely powerful. In just a short while you can get a very bad sunburn, so if you plan on spending a day at the beach you'll need more than just sunblock. You really need some kind of shade as well. Of course you can always rent an umbrella with chairs, but these are quite expensive and you can't move them. I recommend some kind of sun shelter like the one pictured here, which I bought from LL Bean. It worked very well even in the wind and prevented either of us from getting sunburned.
As little as possible that you can get away with on the beach. Good shoes, strong ones with plenty of underneath padding as the concrete of Crete/Greece seems to be extremely hard. Jumper for cooler weather/evenings out of season.
Toiletries and Medical Supplies: Try to get hold of Mijex, mozzie repellant, before they get to you. It is extremely effective. Have tried numerous potions but this is the best and it is not expensive. Another tip, carry it around with you. If you should get bitten whilst over there, as soon as you can get to a pharmacy, as they have red stuff which they will put on for you to stop the bite swelling up.