Wall weapons
Water Park carries the weapons of Infinite Warfare, ported by TheSkyeLord and ProRevenge among others, according to the Workshop page. The page does not list them, and the guides read for this book name only a few wall weapons; no source gives their prices.
M1
In the spawn, by the soul box, according to Sassy Asi.
Hailstorm
Bought off a wall by YaBoyBadger at the start of the game, in place of the starting pistol; good until about round seven in that guide’s words.
VPR
On a wall of the Journey into Space area, next to a perk machine. YaBoyBadger calls it extremely good, Pack-a-Punches it for the escort of David Hasselhoff and buys its ammo on the wall during the boss fight.
Thermite
A Reddit thread finds no grenade on the walls other than thermite, whose kills do not count for the grenade challenge of N.3.1.L.

