A lot of what's been said on here already - DIY, driving, first aid, swimming, make a bow tie etc.
My biggie is having less mental capacity than most people. So when I had enough money for a house deposit, my parents helped me with house viewings, and after I chose a house, they took power of attorney and did all of the legal stuff for me as I wasn't capable of that.
Disneyland Paris planning. My sister arranged it and took me there last time. If I was to go again with somebody else, I would still need help as the park requires a lot of planning e.g. getting a carer, a disabled (green) pass, meal bookings, ride slots, meet-and-greets with cast members etc. So again similar issue to me as with the house buying.