(sigh ... some mothers do ‘ave ‘em ...)
Highland and Scottish Regiments wear glengarries, balmorals, Tam‘O‘Shanters, or Kilmarnock bonnets.
And, yes - that‘s a Tourrie on top - NOT a pom-pom (and, yes - I DO hope the RSM finds out you said that ...)
The tails on a glen are symbolic of the ribbon used to tighten up the headdress (and in hot weather happen to do a reasonable job of shoo‘ing flies away from the back of your neck, as related to me by my grandfather who served in the Boer War)
Irish wear the Caubeen (as already ably pointed out, but I‘m doing a recap ... no pun intended)
I recall the Plough Jockeys used to wear the red beret, but I haven‘t seen them on parade in ages (and, of course, the CF Fashion Co-ordinator would be oh, so offended if they clashed with the Meat-heads)