Favorite is the odd old design Indiana used to use:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=39.729483,-86.264281&spn=0,359.99485&t=k&z=19&layer=c&cbll=39.729467,-86.264394&panoid=QvBI2tFGw_DOCOsM3-ObGw&cbp=12,18.15,,0,16.67 (http://maps.google.com/maps?hl=en&ie=UTF8&ll=39.729483,-86.264281&spn=0,359.99485&t=k&z=19&layer=c&cbll=39.729467,-86.264394&panoid=QvBI2tFGw_DOCOsM3-ObGw&cbp=12,18.15,,0,16.67)
Least favorite is the double height constant slope(?) design now used in Indiana, Ohio, and maybe in Iowa:
http://maps.google.com/maps?hl=en&ie=UTF8&ll=39.867143,-86.048688&spn=0,359.979401&z=17&layer=c&cbll=39.865185,-86.047035&panoid=H6Hcb67lZGEfzBKZfS82Zg&cbp=12,124.13,,0,-4 (http://maps.google.com/maps?hl=en&ie=UTF8&ll=39.867143,-86.048688&spn=0,359.979401&z=17&layer=c&cbll=39.865185,-86.047035&panoid=H6Hcb67lZGEfzBKZfS82Zg&cbp=12,124.13,,0,-4)