The existing one was a galvanized run that hadn't been hooked back up when I installed the new plumbing. It was in bad enough shape I decided to replace the whole run. The first order of business was to unscrew the old valve. I took my big pipe wrench (affectionately known as The Persuader) and put on the pressure. The spigot crumpled, but it wasn't going to come loose without breaking some of my exterior shingles or worse. So I chucked a metal-cutting grit blade into my circular saw and simply sawed it off. Then I sawed the interior run in two. Unfortunately, there still wasn't room to remove the elbow and associated pipe. I couldn't cut it all the way through, but I figured if I sawed at an angle as close as I could get, I'd remove part of the offending threads, shake the whole thing pretty thoroughly, and heat things up, hopefully enough that I could unscrew the remaining coupler. This tactic actually worked, and I was able to remove all the remains of the original run (pictured here, along with The Persuader).
The next order of business was to assemble the new run. As there wasn't room in the wall for a frost-free spigot, I decided to add a shutoff valve with a drain down in the basement. I also wanted to put a drop-ear elbow near the new bibb to protect the pipes from any strain from hoses pulling on it. The folks at the big chain home improvement store informed me that ¾" sweat-to-threaded drop-ear elbows didn't exist. However, I found one at the local independent hardware store, along with a ¾ galvanized street elbow and some pipe dope. I went with a ball valve hose bibb, to avoid all the problems with ordinary cheap stem valves.
Assembling the whole thing required a little forethought. The run through the basement extended along a long crawlspace about 8" high, where I couldn't easily solder pipes. So I made up a short pipe and an elbow on the end of a long pipe, soldered it, and then we maneuvered it into place. Next was to assemble the run inside the wall. After that, I screwed and soldered that bit together. Then came the scary part of cutting into the water line coming into the house and splicing in the new run. Aside from having to juggle everything while standing on slippery mud, it went pretty well. There was a bit of a surprise when I first turned the water back on, as I had removed the drain cap from the new valve while I was soldering it, and had forgotten to put it back on.