Ambush Camouflage (I've heard of people using this with Panzershreck-equipped Panzer Grenadiers, but I've never actually seen it)
Counter-Offensive Tactics
The G43 interrogation function
Not really a thing anymore - it used to provide a damage bonus that would allow two Schreck PG squads with them to kill a medium in one volley, but they fixed that but changing it to an accuracy bonus.
I don't either, but it seems fine to me when I use it. Costs less than a good grenade to get vital territory faster while you're in position for that.
I forget about it all the time myself, but as a free recon function between combats, I really can't see what's there to complain about it.