Board Thread:Warhammer 40k Modeling and Painting/@comment-6078851-20130309150331/@comment-1713318-20130312083528

Those are frag grenade launchers.

In the Codex from the time the mini came out, a Mega-Armour had a built-in Stikkbom Launcha. (I.E. the Ork was equipped with frag grenades in gaming terms). Then they changed the init system for Power Fists/Klaws again, and the Launcha became useless, and was dropped from the rules, but not the minis.