A feature of several species of cat, most notably the Lynx and Caracal genera. Ear-tufts aren't unique to these two genera, though: jungle cats (Felis chaus) and some breeds of domestic cat (Felis sylvestris catus) have them, too, though they're not quite so prominent as those of the caracal or lynx. The actual function of ear-tufts is largely unknown, though in both lynx and caracals, they seem to assist in sensing the direction of sounds.
Among domestic cats, tufts are most common on the larger, more naturalized breeds like the Maine Coon, Siberian and Norwegian Forest Cat. However, they can show up randomly in other breeds too, even short-haired ones, and are even fairly common in Abyssinians. The Chausie hybrid breed often has them, too, but since those are a cross between the Jungle Cat and the Abyssinian, this is hardly surprising.