Paint Carry-on
As well as Mad (flt) scientist correctly pointing out that paint is prohibited on the BA list, if it wasn't prohibited, paint would also be a classified as a liquid. Therefore, even if you were allowed to carry it, it would need to be in a container no larger than 100mls and then no more containers than would fit in the standard 1litre sealable clear plastic bag. If you have 5 or 10 litres of this stuff it would be easier to walk it there!