Mains water valve salvaged from an old washing machine that was fly-tipped at a beauty spot about 3 years ago. I stripped it and took the carcass to the dump. Civic-minded and eco-friendly all rolled into one.
Experimental 12-volt version using a quickly (i.e. badly) wound coil using wire taken from an old home brew motor that was never finished. It works after a fashion, but would probably need a proper tightly-wound coil to be effective. The valve opens when 12 volts is applied, but not fully. The resistance across the coil is about 8.5 ohms which I think is a bit low for this type of coil.
It was an interesting wee experiment and I might develop it sometime if I get more suitable wire.