Dispoportionate leg length. Never been able to bend far enough to touch my toes without dislocating my shoulders (even when I was 9st and 6'2 tall).
Minis I can Drive, Metros I can make move. Corsas cause me pain, and Saxo/106's are absolutley no go. Drove one round the block and had to crawl it, because there wasn't room for me to quickly move from accelerator to brake if I needed to.