Just saw this on the Girl Scout Cookies FAQ:
Q: What are the best-selling Girl Scout cookies®?
A: Our biggest sellers are:
Thin Mints 25%
Samoas®/Caramel deLites? 19%
Peanut Butter Patties®/Tagalongs® 13%
Peanut Butter Sandwich/Do-si-dos? 11%
Shortbread/Trefoils 9%
The other varieties combined account for the remaining 23%