Sable
A recessive agouti gene that allows for any form of black (or darker than base) soft-edged markings found in the natural world (current or past).
Though this excludes mutations to natural markings i.e. melanistic versions of animals.
The gene is not limited to the provided examples.
(sable) Sallander Rabbit - Malinois - Bay Horse
(sable) Siamese Cat - Wildebeest - Port Jackson Shark
(sable qadis) Sallander + Zebra - Malinois + Cheetah - Bay + Thylacine