For exaple items such as the "M14A1 (Camo)" with camouflage paint job similar to that of the "M14 (Camo)", all of the melee weapons, and potentially a lot more items are not possible to obtain from the Vanilla Virtual Arsenal.
The only way to even know about their existence would be to either use mods, play on a mission with a customized virtual arsenal (with those items added to the customized arsenal), or in a "Full Armory" (vn_b_ammobox_sog) supply crate.
Some of these weapons and items are also hidden in the Arsenals from the Mike Force mission and from the Whitelisted Arsenal module.