Itahsa (痛車) as I understand it, refers to cars with plenty of stickers featuring anime characters, usually cute anime girls. I remember seeing plenty of Haruhi, and then Miku themed Itasha in the past. Not just cars, bikes and even bicycles can become Itasha as well.
Read more about Itasha on Quentin's blog.
A very nice Macross Frontier Itahsa featuring Ranka and Sheryl was on display at the recent Macross F Galaxy Tour Final (thanks to rpt011r for the translation).
There are also model kits of Itahsa, but I can't seem to be able to find any information about them though ^^;
Everyone's favorite trio of girls from Macross Frontier ^^
Other nice goodies you can get from the event:
HGIF Macross Frontier Characters - All four types, six figures per set. December release. Price from HLJ is 2,400 Yen.
Macross Frontier Character Box - 8 figures per set, each figure is about 100 to 110mm tall. All five types. Late January release, 5,460 Yen per set. More photos in this previous posting.
Ranka Lee cookies? ^^
Ranka's giant salamander friend XD
Can drinks that can help you to sing well? XD
Ranka's special Tofu?
Special magnetic card I think...
Souvenir pack from the event.
All images from Jabro's Rumors of the Wind (Itasha, other merchandises 1 and 2) and Toybu Dotnet.