Here are some examples of KeyMod’s on other weapons.
Barrett 98B Fieldcraft
Shown on Euro Optic.
ACR Forum user mrtoyz has a prototype posted.
There is also an ACR airsoft version called the S.L.A.S.H. (Super Lightweight And Slim Handguard).
VLTOR makes a version of their CASV as a KeyMod as well as the optional extension, also available in black or patriot brown.
Shown on a Japanese site, the real deal?
Prototype from Wojtek Weaponry shown on The Firearm Blog.
I know I said no AR’s here, but these can’t use the conventional AR handguards due to the piston assembly. H&K with KeyMod and OSS suppressors.
Strike Industries has shown off two handguard concepts for the MR556A1.
Shown on Guns & Ammo with a chasis incorporating the KeyMod slots.
Shown at SOFIC as a factory concept.