My favorite helmet would be a toss between the Orcish helm and the Jagged Crown. Its looks real boss on some characters. I also like the Dragonscale helm for its unique shape.
The dwemer helmet
I love the fur helmet. Granted it's not as good as the Oblivion one, but I still HAVE to wear it!
Masque of Clavicus Vile. Because it reminds me of a Spanish Conquistador Helmet. (Which Who I am descended from.)
because i use khajiit mainly, its dragonscale helmet.. it also look awesome for argonian :)