There are probably a hundred different options depending your requirements of security vs. convenience. By "others" are you talking about little children, nosy family members, amateur thieves, etc?

The mechanical simplex locks on the above safes are very convenient, but their weakness is you can run through every possible combination in about 15 minutes, maybe less. So it might be secure against little kids, but if you have curious teenagers around I'd be worried.

These are also pretty popular

http://www.gunvault.com/

But again it's just a deterrent, a few simple hand tools can defeat it pretty easily. No matter what kind of safe you get, it has to be bolted down otherwise someone will just walk off with it.

I have this wall safe with electronic lock, I believe they also make a smaller size

http://www.walmart.com/ip/Mesa-Safe-Co.-Electronic-Wall-Safe-20-H-with-Two-Shelves/11402214

It's not real secure, but a great value for the price. As you said, the more concealable the better. Security through obscurity, if someone can't find it, they won't be trying to open it. It does require more work to install but the compromise between security vs. accessibility is perfect for me.