Not look like a lobster

Nivea

Unless you're playing indoors, you're going to be exposed to the elements and even when it's cloudy you can burn without realising it. 

Protect your skin from the sun by applying sun cream before you head out onto court. Use a water (ie sweat) resistant, non-greasy cream, and if it's a scorcher go for a cap and light wraparound sports sunglasses too.