Gravy in sachet form. Is accompanied by what many consider to be the best ad ever made. Sounds a little like Gravy-Ox.
Also used as a good-luck exchange between friends. Often accompanied by a raised fist.
This is Gravy. This is an Ox. This is Gravy. This is an Ox. Gravy. Ox. Ox. Gravy. (sung) "gravox, it sounds a little like gravy-ox"
(before an exam) "Gravox!"