Horns in animals and birds
Males of the carnivorous Jackson's chameleon (Trioceros jacksonii) have three hornlike structures on their heads (also found in a couple of related species). From what I know, these are true horns, which means that they are pointed keratin-covered protrusions that have a core of living bone, see e.g. this website from Toronto Zoo (this page also claims that their horns show annual growth rings). However, there are many definitions of horns (some only consider the horns in Artiodactyla to be "true" horns), so you need to be specific in what you are asking for. Used casually, the antlers of Cervids or other similar structures, are often considered as horns.



As for birds, the closest thing to a horned bird I can think of are species of the Australian Cassowary (Casuarius). They have a bony crest on the top of their heads, which is covered by keratinous skin. However, the bony crest is supposed to be relatively soft and spongy, and can hardly be counted as a horn is the strict sense of the word.


(Southern cassowary, Casuarius casuarius, from Wikipedia)