We use this Wichard key-pin w/bar shackle:
Wichard Shackle - key pin with bar 81434 Sailnet.com - community, sailing resources, shopping, sail, blogs
It can be opened by hand but it requires strong fingers; so it should not open while hoisted. The pin is captive so you don't need to worry about it falling out when open. The pin keeps the shackle from turning sideways while hoisting. Easier than using a shackle knife each time you stow the halyard. I don't like the similar Ronstan product because I have seen them self-open when well-worn.