I suppose anything thats been out of production a while could be deemed collectable, not only old guns really as one that is pretty modern is the Pro elite which I would say is definately entering collectable description, as are your you Sussex Armoury military style rifles, early AA to such as Carmargue and the like
BSFs are another fine example, and Roger on here has an impressive collection along with an impressive knowledge about them should someone need some
Then theres I.Js era such as Pattern Ds, and BTDT has a fine collection of ball chamber pump ups from the 1700s which he regularly takes out Rabbititng
Baz