Hello Steve,

I am absolutely sure that you will get many different replies to this question but I will give you mine.

If it's the last shop you visit, you should certainly visit Eisenbahntreffpunkt Schweickhardt in Waiblingen near Stuttgart. Biegelwiesenstrasse 31, 71334 Wablingen-Beinstein.
They moved into these new premises in 2000. It is a new, custom built model railway shop, absolutely fantastic selection of gear, lovely people, good parking and ease of access if you require it.

If you look on their website now www.modelleisenbahn.com they have a little map of how to get there (because there is a bridge reconstruction nearby).
The zoomed photo, or if you look on Google maps, also reveals the large area outside the large, single-storey shop for garden railways with layouts of several gauges.
Awesome place to visit, you could spend a day there.

If, on the other hand, you want to poke around in a little old shop that seems to go on forever with treasures on every rickety shelf, to find rarities or old collectable second-hand stuff as well as all the latest list items, then I would say Modellbahn Ritzer on Bucherstrasse in Nuremberg, or if you are near Stuttgart, Modellbahn Seyfried in Pforzheim. Both are real Aladdin's Caves of treasures beyond your wildest dreams!

Just my personal view, I am sure you'll get many other suggestions.

I sincerely hope you get the trip together.

best regards

Phil