[Rumil]

I always wondered if Aiglos was more of a lance, I could imagine Gil-Galad on a splendidly caparisoned charger weilding a rather special spear, probably with a bue and white (or silver/mithril) pennon. I guess you might say this theory would fall down if he couldn't get his horse up Mount Doom, but there you go.

On the other hand the spear could be dual-use, ie useful on horseback or dismounted. Certainly the Rohirrim seem to have done this and it was viable historically.

Cirdan or Elrond probably half-inched Aiglos if it survived when Big S went up in smoke, as they were the only two left with Isildur at the time (whose attention was taken by a certain shiny ring of course).