3V6, 3V9, 5V1, 5V6, 6V2, 9V1, 12, 15, 24V are all that I commonly have used, The rest of the time you can just use 2 or more in series, and get the odd voltages. Note as well that anything below around 5V will be very poor, the kbnee on low voltage zener diodes is so gentle that you will get around 1V difference with current.
I did buy a box ( 10 000 of each value) of 12V and 24V 400mW zeners on auction once, so I have a lifetime supply, so I use them as regular small signal diodes. IIRC I paid $2 for the lot.