On a recent trip to Germany, I found this shop to go way above the usual level of service.
The shop has a fairly large inventory, rents bikes, and does transalp tours. It's also located a quick four block walk from the train station.
This shop is open on Sundays in a country where many supermarkets aren't even open on Sundays! This was important to me, as the trip I was leaving on left very early Monday morning, and I had arrived in Garmisch Saturday evening.
The owner was the only one working that Sunday. Before I had spent a penny in his shop, he let me borrow tools, didn't mind that I worked outside the shop, and was generally very helpful. And this is in the context of Germany not having very good customer service in comparison with the US. I have been in many of the other shops in Garmisch-Partenkirchen, and didn't find them lacking in any way, but did find this shop exceptional enough that I don't hesitate to give it a strong personal recommendation.