3.5" bazookas last time I checked – would like kneeling and firing, and prone and firing poses.
Prone and firing WWII MG42 team for the Pendraken range. Summer and Winter dress. Can't recall if Minifigs does one.
ATGMs especially: SS-11, Bantam, Cobra, Entac, Swingfire, Sagger, Snapper, Swatter, HOT, TOW, etc., etc., ATGM ground mounts with guy controlling them. Man controlling them probably separate from the weapons, where appropriate, since some permit the launcher to be quite some distance from the guy controlling the missile.
"In-flight" ATGMs to go with the above.
Could use some Dragon gunners in various poses, prone and firing; sitting and firing, carrying the weapon.
West German RPGs – PzFst 44, and later models.
MG3 prone and firing, with troops wearing olde-style, US M-1 helmets – works for West Germans, many NATO countries, and various others around the globe too.
Guys walking/searching with hand-held minesweepers.
Guy with a control box, either standing or kneeling/sitting, and an aerial drone – perhaps one on the ground next to him, and another separate to be mounted as if flying. Most of the early ones seem to be the olde-style, model airplane type drone, but you could also do the quad-rotor helo-type ones too, I suspect.