...items covered to some level:
UK:
AEB bomb thrower, Arbalest, The Bombard Experimental Gun, Bombard, Hedgehog, Hedgerow, Water Hammer, Mustard Plaster, Baby Bombard, Jefferis Gun, Stewblack Projector, PIAT, Petard, Denny Gun. CLarke Family (Tree, Ground, and Gun).
US:
US Tree Spigot, Bigot...