!!OpenXcom Extended is Required!!
This simple mod adds a weapon much like the OICW - a light autocannon with an underslung rifle, buyable from day 1. It's a mite expensive, stupid heavy for a rifle, and a bit unwieldy for room-clearing. As explosive weapons go it's a scalpel: not as indiscriminate as a rocket launcher and a much straighter shooter than the cannons. Just don't mistake the rifle part for the main attraction!