11″ MacBook Air
Being that I travel enough (I used to travel a lot more!), I have used a laptop since I went on the road with Hypnotic Clambake in 1995 (with my first laptop, a PowerBook 520c). Starting in 1998 and up through 2011 I used a laptop as my main computer. It was easier than spending a day on either side of any trip copying data back-and-forth to my laptop. By 2011 (and indeed, for quite a while prior) syncing services and technologies such as IMAP, Dropbox, SugarSync and more allowed me to maintain my data between two (or more) computers without much issue. There was no longer a reason to make my laptop computer my main computer and at that point I moved to an iMac. That also allowed me to make my laptop a purpose-built machine that was just for travel, and with that I now use an 11″ MacBook Air (and love it).