Germany

Schadenfreude

Zeitgeist

Kindergarten

I prefer English words making it incorrectly into German. "Getting a handy from your buddy at a public viewing" is totally innocent in German.

My friend in Australia is a doctor studying psychiatry and he kept asking me what certain worlds meant and half the time I had no idea what they were or how to explain them lol.

Very random. Here's a wiki list but I remember there were some others too

Anwesenheit

Dermatozoenwahn

Entgleisen

Gedankenlautwerden

Mitgehen

Mitmachen

Pfropfschizophrenie

Schnauzkrampf

Wahneinfall

Verstimmung

vorbeigehen; vorbeireden

Witzelsucht

Würgstimme

Word salad/Wortsalat

Zeitraffer

Zeitlupenwahrnehmung

It's kind of interesting to see the long lasting effect of Germans pioneering the medical field for a very brief time in history.

I think doppelgänger is the most spread one.

Gesundheit

Poltergeist

Spiel

Stool ( Stuhl )

Rucksack

For the chess people: Zugzwang and Zwischenzug!

Zeitgeist

Spiel

Schadenfreude

Kindergarten

Iceberg

Eigenvalues and eigenvectors, which however, were not discovered by the well known mathematician Eigen. Ansatz ist also commonly used in research articles.

Gift. No wait

I guess mine would be kaput

As an American: Hamburger

(German) Angst Apfelstrudel Kindergarten Oberlichte ...

Meister

Gestalt

Bremsstrahlung

In mathematics:

Eigenvektor

Halt!

Abseiling

Zugzwang

Abseil.

Doppelgänger

Weltschmerz

"Ouch"

Nagelbrett. https://coenbrothers.fandom.com/wiki/Nagelbett

Does "Neuschwanstein" count? As in the castle in bavaria. Because I find it amusing how native english speakers just stumple over the pronounciation. Also "Gesamtkunstwerk" because it seems kinda superflous.