: Unfortunately, Jackson's hobbits are dressed in medieval clothing, and I guess we'll have to wait and see if they have clocks. In general I agree with Martin's comments, although the Guards of the Citadel should indeed have an Egyptian look and feel to their helms (they're wearing chainmail, so the Norman knight comparison, conceded by Tolkien, is acceptable in that respect).

Big excision:

The ancient Egyptians weren't very overt with their helmets. Indeed, until the Hyksos invasion there is little evidence for them at all. The only helmet much shown is the Blue or War Crown of the king himself - which doesn't resemble those of the Tower Guard in any real way. Most Egyptian helmets seem to have been simple bronze skull-caps worn beneath their traditional head-dress (hetef?) - the stripey cloth with stiff folds. Other Egyptian helmets seem to be composite affairs made of overlapping bronze scales attached to some sort of underlying frame.

The closest parallel to the descriptions of the helmets of the Tower Guard (ie tall, pointed with wings attached near the browband) would be the mythical winged helmets of Viking romance.
For real helmets the closest would be representations of a type of Celtic helmet with a elongated conical skull and cheek pieces which is known sometimes to have had wing-shaped ornaments attached (excavated examples, plus bas-reliefs on the Roman Arch of Orange in France). Another contender would be a type of Italo-Greek "Attic" helmet much used by the Samnites and other southern Italian peoples which had large bronze wings attached, though as the skull was rounded, not pointed, the parallel with the Dunadan helmets is not as great.