Balrog,
They aren't that uncommon. A good number of folks who are recoil sensitive use 20 gauge Remington 1100s for HD, and the newer youth model 20 gauge 11-87 is attracting a certain following as well.
There are other contenders- the FN SLP is a good shotgun, Mossberg's 930 has its fans, there are a goodly number of older Browning Auto-5s and Remington 11s still on the job. Of course there are a number of other designs/makes/models still going. Older Benelli M1S90s, Beretta 1201s, all sorts of things too numerous to mention.
If you want a semiauto, I'd suggest getting one that's still in production so you have accessories as well as parts support in the event anything goes wrong (not that it's likely to), or getting something recent enough or popular enough that getting it worked on/accessorized to your liking is not such a big deal. There's no need to assume any less reliability for a good semi with good ammunition than for a pump gun under similar circumstances.
fwiw,
lpl