Oh there are lots of helmet types which were actually used in warfare. The Greeks had many kinds, such as the Thracian and Beoetian types, each of which had pointed or extended tops. The simple and practical Pilos helmets often had wings or horns added to them. Similar things are found on Samurai and Persian and Indian helmets. Constantine's "Cornuti" soldiers appear to have had horned helmets. Although an added feature like a horn, plume, or wing may not have any direct effect in terms of providing defense, these things were very useful for maintaining command, and for knowing who-was-who in the chaos of battle.
