Th I have just finished a lovely aviator style hat for my grandson Alexander. This one buttons up under the chin and covers the ears so a good choice for the colder weather. I've used the same grey and blue 8ply woolen yarn in a previous jumper knitted for him so he now has some lovely coordinated clothing. The cables are very easy.
The design is by Julie Taylor and it's called the Dayton-Cabled Baby Aviator Helmet. This is the link if you would like to purchase the pattern: http://www.ravelry.com/patterns/library/dayton---cabled-baby-aviator-helmet
Grandmother and knitter from the land down under of fine merino wool.