I sold my H&K SL6 a few weeks ago for pretty much that reason. Great gun but too rare and too pretty to be much more than an occasional range toy and safe queen. Funny thing is I bought it for $1600 off a guy I know. I turned it around on Gunbroker and sold it for a little over $2600.
I like guns that I'm not afraid to use in the rain, snow or any whether condition.
The only gun I have now that I would consider really pretty is my Anschutz 164, however I don't consider it too pretty to shoot on a regular basis.
As for handguns I've owned two in the past year that I decided were too pretty to keep. Both were Walther P88's and both were in immaculate condition. I bought them both around the same time and it was long after that I decided they wouldn't serve much use other than just being safe queens. I didn't want to get them dirty or risk holster wear by carrying them and I figured what's the point of keeping them if all I was going to do was look at them. So I sold them both and used the money to fund guns that would serve more of a purpose in my collection.