The first helmet I bought was a full face helmet. Shortly after, I bought a half-helmet to get some wind in my face and later on, when the padding closest to my forehead was wearing out, I bought another half-helmet that I have liked a lot (Z1R Nomad).
A couple of months ago I saw the Fulmer booth at the International Motorcycle Show and really liked their 3/4 helmets (Fulmer V2). They're DOT approved and have less of a spaceman look than most modern 3/4 DOT-approved helmets. I went online to buy one and quickly realized you can't buy them anywhere online. I ended up finding a local shop that carries them (Blue Cat Motors), tried them on again to ensure I got the right size and had them order me a gloss black one. The helmets do seem to run big as I tend to wear large helmets but needed an XL Fulmer.
So far I've really liked it. With the weather being less than perfect (windy and/or chance of rain), I have attached a NOS clear bubble shield from Lowbrow Customs. They warn you on their website but these NOS bubble shields really do stink (strong plastic smell). Mine has aired out for a while and is a lot better than it was. You don't notice it while riding but sometimes can still smell it when stopped.
Anyway, here's a pic:
EDIT (6/14/10): Wow, it seems a lot of people are trying to figure out where to buy these things. As mentioned, Fulmer helmets are not available anywhere online and that is deliberate because Fulmer wants you to ensure it fits. You can find a local dealer by going to Fulmer's dealer locator here. Also, Fulmer makes their own line of bubble shields in clear, smoked, bronze, and chrome. You can see them on their website here and I assume you can order them anywhere the helmets are sold. Like I said, I got my vintage bubble shield from Lowbrow but I can still smell it months later (I don't care because I really like it). Other manufacturers make bubble shields too. A new one would likely have less odor but what fun is that? I did find this site with bubble shields for sale but have never dealt with them. Good luck in your search.
EDIT (10/18/11): Biltwell just started carrying their own line of bubble shields.