Not just gasoline.  While opening a plastic quart bottle of algaecide,
tearing off the little paper inner cap, my husband got a very strong
electrical shock.  He didn't know what to make of it but after it happened
twice more in the same day, he called the chemical manufacturer who said
that they were busy tracking down particular batches of this stuff. 
Apparently while being filled, these bottles run on a conveyer belt and
tend to rotate around, building up static electricity.  The belt not being
grounded, stores the static within the liquid which remains there forever
until someones fingers touch the foil lined paper seal which conducts it
out of the bottle and through the unsuspecting person.  My husband works
with electricity quite a lot and has gotten "bitten" a few times but he
said this was a real good jolt.  So I guess static, plastic and any liquid,
just don't mix!

Wendy & John
'85 Westy,   "S-CAPE"