It's hot, even in winter here- If you're here in winter just get a light sweater.
Toiletries and Medical Supplies: Muscat is a city- you'll find anything you need here.
Photo Equipment: Bring a camera and film, lots of beautiful scenes.
Camping/Beach/Outdoor Gear: Camping and beachwear. Plenty of nature bonding here.
This tip goes out especially to travellers from small countries like Malaysia. It is virtually impossible to get Omani Riyal in Kuala Lumpur, and money changers in Muscat rarely accept MY Ringgit.
DO make sure you bring major currencies, or change your currency in Omani Riyal at Dubai airport.
There is a money changer before passport control but again, they don't accept ringgits, and you don't want to waste time losing your place in the queue for passport control. Have at least 6 Omani Riyals for your visa (in local currency only).
Toiletries and Medical Supplies: Bring you own suntan lotion. The Seniorita Moisture Sunblock I bought at the souq was bad. I was freaked sunburned by it. And it was the best suntan lotion they had... Oman is not Dubai...