i think mostly languages. So you can do as stated above an A level in Arabic or Greek, Hebrew and Turkish. You can also do Welsh or Irish which is obviously more common in Wales or Ireland (ik they are not that uncommon but no one takes them outside of Wales or Ireland really and i think they are pretty cool A levels).
You used to be able to do a Cornish A level (or equivalent) but i dont think that exists anymore which is quite sad.
You can do world development. Journalism, product design and Artificial intelligence are A levels.
Havent done any of these, just had a discussion with my friends not that long ago so we looked up a couple and found out AI was available.