Sounds like the OP started by asking for opinions of the best general gunsmithing vise, but then quickly added a query for input on other types of vises.
Last night, I took a little inventory of my vises. I suppose that if I can use them for a gunsmithing type operation, then they could be considered here. In my opinion, there is no one single vise that is great for all things, just as I have different guns for different hunting or shooting activities. For example, a checkering cradle is a sort of specialized vise used to firmly hold long wooden gun stocks at different angles during checkering. You could clamp your stock in the padded jaws of a machinists vise, but it would be far from perfect for checkering.
In my shop, my most used vise is a 4" L.S. Starrett Model 924 Athol Vise that currently has a pair of 4 1/2" copper jaws installed, that were milled out for me by a tool and die-maker friend. It has a swivel base. Athol, Mass., U.S.A. made of course.
It's little brother, an L.S. Starrett Model 923 Athol Vise is on the workbench in my basement. It has a non-swivel solid base, and 3" jaws. These Starrett's are extremely well made. Then I also have a nice, heavy old Reed No. 204 1/2 swivel base vise with 4 1/2" jaws. On the steel plate top mounted on my Kennedy roll-around tool box is a U.S.A. made Columbian Model D55 with 5 1/2"jaws. A roll-around toolbox is hardly an immovable mount, but it is very handy and useful nonetheless.
A drill press is almost indispensable for gun work, and I have several drill press vises to hold the things I'm drilling. On the table of my Rockwell floor model drill press is a Heinrich Tools, Racine, Wisc. Model 20A 6" that opens to over 10". For smaller stuff, there is an unmarked 4" wide vise with a low profile that I believe came off of a milling machine.
On the table of my Delta bench drill press is an old Craftsman drill press vise, and I also have a well made 3 1/4" Japanese import with an X and Y axis crosslide. I also recently picked up a nice little homemade 2 1/2" drill press vise from a local guy who sells surplus tools and equipment for $2.00 a pound. It is well machined, and may have been a project done by an apprentice machinist or tool and die-maker. It was too cheap to pass up.
Then there's the cute little 2" machine vise that is made by American Edestal and came with my Unimat Lathe-Mill-Drill. It has come in handy for a number of small gunsmithing projects, and in this application, my big heavy Reed or Starrett just wouldn't be any use at all.
I also have a couple of those small clamp-on vises like Stan mentioned. The larger one is surprisingly well made and quite sturdy and heavy for it's 2 1/2" jaw width size, but it is unmarked. I'd say it is U.S. made judging by the quality. It belonged to my grandfather.
I have three Ridgid Pipe vises, and my Grandfather's old Reed pipe vise. Two are pretty large, and one is mounted on a Ridgid folding tripod stand. Then I also have a nice portable Ridgid chain vise.
Wait... there's more! I have a little Pana-Vise with a ball swivel. It is great for holding small parts, circuit boards, etc. at different angles during operations like soldering. I think it is made of die-cast aluminum, and it certainly isn't meant for hammering or blacksmithing type work. Then I have an unusual Stanley No. 700 woodworkers corner vise, a 7" Wilton woodworkers vise, and an unmarked 10" woodworkers vise.
Some other must-have gunsmithing vises that I have are several hand vises. These have fallen out of favor for some odd reason, so most are now collectible antiques. But they are as useful as ever. I have several pin vises too, for holding screws or pins during grinding or polishing. There are some hand vises pictured in Daryl's current "Tool Mystery" thread in the main shotgun forum.
A vise is no substitute for a blacksmith's anvil. I learned this the hard way when I broke a good vise years ago, hammering on something with a sledge hammer. When I wish to press bearings, etc., I use a press. I have a small Greenerd No. 1 Arbor press, a larger Dake No. 0 Arbor press, and a Blackhawk Hydraulic press that currently has a 10 ton ram cylinder, for those tasks.
I'm sure I've forgotten a few. I know there's some large imported monstrosity swiveling jaws Versa-type-vise-on-steroids on a shelf in my shed. I inherited a few of these vises. But my best purchase deals came from car parts swap meets and flea markets. Auctions can be good too if the crowd is small due to horrible weather... the best time to go to an outdoor auction is when it's so nasty that nobody wants to go... but the really nice vises typically get a lot of bidding activity, and sell quite high.
There are some great vises pictured in this thread. Even though I have more than enough vises, I still get vise envy.
