Products known just by letters and/or numbers. Like Z28 (I'd love to have a '79 Z28), A-1 sauce, 7-Up, etc
Cutaway ads, those ads that 'cutaway' and show the inside of a house of building and are, in my opinion, just fascinating.
Funeral related ads. Cheerful!! :) There's a plethora of such ads in the late 1800s, tho you can find some in the 1900s. But during Victorian times mourning was an art form in a way.