I know people that would easily get sun burnt on their nose. I suppose certain parts of your body would be more sensitive to the sun but I'm not certain what causes that. hoping someone with more knowledge and chip in.
I apply sunscreen to all parts of my body if I'm going out to the sun for long periods of time. I haven't noticed certain parts of my body being more sensitive than others either.
slight tangent: Dermatologists all recommend against tanning and especially recommend wearing sunscreen if you're going to be at a higher than 3/4 UV indexed sunlight for prolonged periods of time. It damages skin and encourages skin cancer.