Day trip from Nurnberg: Rothenburg? Regensburg? Other?

Rothenburg would be my choice.

Other possibilities include Bamberg and Bayreuth (Wagner country)

Coburg. It has, in my opinion, Germany's best castle, and the Altstadt is stunning. Unlike Rothenburg, it isn't filled with trinket shops. If you drive from Nürnberg, the route is rather scenic. You could also include a brief stop-over in Bamberg, although you won't have enough time to thoroughly explore both.

RE- Bayreuth. Wagner's Wannfried villa is closed for renovation, so if Wagner is the only reason for a visit, you may find the city a bit of a disappointment. When I visited, it took me a little while to warm to Bayreuth.

The charming old walled village of IPHOFEN is in Franconian wine country about 45 minutes northwest of Nuremberg's main station by direct train. Here's Iphofen's TI office brochure.

If you want to see Rothenburg (and hordes of tourists) R'burg is roughly 1.25 hours each way on 3 separate trains.

For travel to either town, you can use the VGN Tagesticket Plus day pass - it's good for 2 adults and costs just €17.50 per day. It's actually good on 2 consecutive days if the first day is Saturday: VGN Tagesticket Plus

Bamberg is also a fantastic day trip from Nuremberg - and about 45 minutes by direct train as well. The VGN pass will also get you to Bamberg or to Bayreuth.

For Regensburg, the VGN pass doesn't work - get a Bayern Ticket (€27/2) instead.

Another town, with an almost intact wall, is Nördlingen. You can get there from Nürnberg in about 2 hours with a change in Donauwörth. It's a lot less touristy than Rothenburg - lacks a Christmas shop and Crime and Punishment Museum, but you can walk on the top of the wall (Wehrgang) and climb the church tower, plus it has many Fachwerk buildings. I spent almost 24 hours there on my Romantic Road trip in 2007 and hated to leave.

About 20 minutes south of there by train is Harburg, with an intact castle, but there is no public transportation from the station south of town. It's about a 1 km walk.

Ingolstadt, about halfway between Munich and Nürnberg, has a quiet, picturesque old center. Among the attractions is the German Museum of Medical History, in an 18th-Century building that formerly was the Anatomy Building of the University of Ingolstadt. The gardens in the courtyard are made up of medicinal herbs and plants. The building is more well-known in literature than in real life, as it was the setting of Mary Shelley's 1818 novel, Frankenstein. The Audi factory is just north of the center, and factory tours are available.

Download an Ingolstadt walking tour here; photos here.

Here's my favorite easy day trip from Munich: Take S8 southwest from Munich to the end of the line at Herrsching. Walk 500 meters to the pier on the lakefront. Take one of the elegant century-old paddle-wheel steamships across the scenic Ammersee to the authentic, untouristed lakeside town of Dießen am Ammersee. Wallk through Dießen to the ornate Marienmünster abbey (1732) that overlooks the town.

Return to Herrsching, and take Bus 951 (or hike about three miles up into the forested hills) to Kloster Andechs, where the Benedictine monks have been brewing beer since the 15th Century. Photos here.

For something completely different, go about an hour west of Munich to Bad Wörishofen. It's a spa town, birthplace of naturopathic medicine, and home to a large spa/sauna/pool/waterpark complex. Plan your trip there on a Sunday, and go to the small grass-runway airstrip on the north side of town. Sit at the open-air café on the field and watch the skydivers and ultralight aircraft, and wait for your scheduled 45-minute flight over Neuschwanstein or the Fünfseenland in a classic Russian-built, 11-seat, 1958 Antonov An-2 biplane (advance reservations necessary; info and reservations here; photos here).

BAMBERG! It isn't a small town like some of the others, but it's a short train ride from Nuremberg and ridiculously beautiful. During the 17th century a local ruler gave residents a tax break if they had their houses baroqueised, and many of them took it up. Because it was very briefly an important place around that time, and then declined again, it went through both World Wars almost completely undamaged. (I visited a friend there a couple of years ago, and she showed me the memorial where the ONE BOMB that hit the historic part of the town landed.)

I'm not a beer buff, but it's also famous for its breweries.

We enjoyed daytrips to both Bamberg and Regensburg when we stayed in Nurenberg a couple of years ago. Both are an easy train ride, maybe around an hour each way? Both towns are lovely and easy to walk for a rewarding day trip. If I had to choose one, I guess I'd say Bamberg but both were great.

"I'm not a beer buff, but it's also famous for its breweries."

To explain a little further, Bamberg specializes in the production of Rauchbier, meaning "smoked beer". I can happily report that it's a good smokey flavor, like smoked meat, and not like a cigarette after-taste. I've looked and looked in my area of Germany, but I have not found any of these available outside or Bamberg. You really have to visit the town to try the beer. So, if the idea of a smoky-tasting beer paired with some Schweinhaxe and Knüdel appeals to you, a trip to Bamberg may be worth it (but I still recommend giving Coburg a look-see too).

BTW, I noticed hiking is also on your list. You may also want to consider a visit to the Frankische Schweiz (Franconian Switzerland) region to the north and east of Nürnberg. Despite the name, in my opinion, it looks nothing at all like Switzerland, but it is quite scenic in it's own way. You would probably need a rental car, however.

Thanks so much for all the recommendations! Many look like great options. I'll enjoy doing research to figure out which one is the right one for my trip. Thanks again!