Although not unheard of, I can recommend the sight of a 'glory' or 'Brocken spectre'. It is best viewed from atop a mountain, usually in winter, just before sunset, with your shadow cast onto a nearby cloud. The resulting spectre has a halo radiating from its head. You can only see your own halo, not that of anyone with you. I will try to attach a pic I took last year from the top of Slieve Binnian. If it goes wrong (new poster) I will put it in the gallery instead.