I do not remember that happening. Are you thinking of a grease gun?

One of the few pieces of Axis equipment regularly used by American forces in Western Europe, the Panzerfaust, demonstrates why other Axis equipment was not used regularly. The Panzerfaust was a man-portable anti-tank weapon that was easier to use than its Allied equivalent, the bazooka, and much more portable. The Panzerfaust was also better than the Bazooka for use against hardened bunkers and could be easily stowed in a jeep for emergencies. Its one-shot use meant that the issue of resupply was not an factor. The one-shot and small nature also meant that it mitigated the issue of friendly fire as it was both concealable and its audio-signature was not repeated once fired, unlike, say, a captured machine gun. In short, the Panzerfaust did its job slightly better than Allied equivalents and its one-shot design mitigated the usual problems associated with using foreign equipment.

In Kershaws' 'It never snows in september' on the German perspective on operation Market Garden a German soldier is quoted saying : '... after two or three days it was no longer possible to identify friend or foe from the firing of weapons. Ours fired faster generally than the British. But both sides used each others.'

The German soldier says that they preferred the sten over the schmeissers as the magazine fed sideways and could be refitted in the prone position and thus made reloading a lot safer. The Germans had plenty of access to English ammunition als 90% of the English supply drops were dropped to the Germans as they had found the smoke signal/light signal system to indicate the dropzone on a dead officer.

Alternatively Phil Nordyke in his book 'All American, all the way' on the 82th airborne has a soldier claiming that the Americans preferred the German schmeissers over the thompson smg for street fighting in Nijmegen as they were better at penetrating the doors. He recalls the German dead being scavenged for their ammo.

So basically: It depended on the situation. The German soldiers were often under-equiped and took whatever they could find and found the English weapons to be superior to their own, certainly considering their loading meachanism. The Americans found the German weapons to be superior in the particular style of fighting in an urban environment.

Basically all soldiers would scavenge what they could get their hands on, the difficulty was in getting supplies. Superiority depends on the role one is playing. In defensive positions it may be better to not have to raise your body to reload, but in urban environments the same weapon might be considered advantageous.

Were the German weapons actually superior?

On the Eastern Front, no. Often German weapons suffered from a very unique German problem -- over-engineering. That means the design simply required way too much maintenance or the weapon may have worked well in testing conditions, but once in the field, the weapon would jam far too often.

And with Russian engineering -- simple but made to work. That meant with a much simpler design, there are fewer things to go wrong. And with fewer things to go wrong, the weapon can work much better in the field and requires much less maintenance (and most people hate doing maintenance).

Likewise, we could say the same for the feared German Tiger Tank. It was a massive thing and it did work really well -- when it was working. When it broke down, then it became a mess due again to over-engineering.

Regarding the Eastern Front -- I would recommend Anthony Beevor's book 'Stalingrad', about how in the total hopeless situation, German troops would resort to using the Soviet weapons since they simply caused fewer problems.

I hope it's okay to reply with a related question. But I wonder, if they did pick up enemy weapons, could it be because they'd be more likely to find extra enemy ammunition and less likely to be resupplied with their own, as they advanced?