The rarest is the red MV. The next rarest are the red MM and the blue WW, WC, WH. Then blue WU, HX and red YC, XC. The rest are fairly easy to find. Reds are a lot more common than blues.
Error OPAs are worth a little more. There is a good example at the end of this page.
Tokens used for rationing during World War II
There are 30 different red tokens and 24 blue ones.
They are all vulacanized fiber (celluloid) and 16mm in size.
Blue ones read: OPA Blue Point 1 (with two different letters)
Red ones read: OPA Red Point 1 (with two different letters)
**SPECIAL** Complete set of the above blue OPAs $32.95
Canada Meat $2.00
ERROR OPA'S
Red YV (minor off center) $1.50
Red ?? (Very rare - Way off center - Only the top of a R on one side by edge. The other side is bottom of P.) $80.00
Blue YY (minor off center) $1.50
The following is an example of an error OPAs. The pictures were sent to me by Dan Orbeck. As you can see OPAs can be struck, by mistake, more than one time. They are also not always centered when struck.