As I'm going through a bit of a artillery phase at the moment this wonderful Soviet 100mm field gun by Piers Brand over at World War 20mm.
Although designated a 'field gun' the BS-3 was, of course, a very successful anti-tank gun and I guess you could put it in the same class as the British 17 Pounder.
Once again, despite this being a war gaming piece it is mounted on a mini-diorama base. I am coming round to this idea as while some war gamers don't base their guns so they can fit them into tight spaces on a table I was swayed by the line of thought that says such guns needed space to deploy so a base is just a realistic means of stopping people hiding guns in crazily small locations. Well, that's the theory - I just think they look nicer!