The Incident at Quiliam
A 7 (or 3, if you only count the action levels) level scenario. Nice attention to detail, it'll keep you on your toes. There are always shots coming from somewhere...
Levels in map "The Incident at Quiliam":
U.E.S.C. Bustard
Transport
Quiliam Weapons Complex
Transport
Masabesic Treatment Plant
Transport
U.E.S.C. Bustard