Anti Fog Spray Recommendations?

I've seen people mention anti fog spray on here before for goggles.

Can anyone recommend a particular brand?

Is it necessary to go for a 'cold weather'/ski designed spray?

Does it work on sunglasses as well?

Thanks in advance :D

The spray I've used for years is Hilco Fog Buster. I use it on spectacles and ski shades. A bottle lasts for utterly ages. I get mine from these folks.

http://www.gosportsspex.co.uk/ZeroFog.asp

Thanks Bandit. I'll get some ordered.