I have two of these (the 200):
http://www.gunvault.com/gun-safes/nano-vault.htmlI use the cable rather than bolting it in place. I carry it when I fly and cable it secure in the room. It isn't perfect but it will prevent a lot. I have tested it before I started recommending it, and two of us could not break it free from its cable when the cable was wrapped around the pickup seat frame. It is great for the smash and grab, portable security, and even quick security within the home. If you want it permanent you can bolt it to anything.
I recommend for the portable you stick to the good old fashioned key. Mine lives in my pickup, and I have never had an issue working with the key, but another instructor I work with has fouled his combo style and biometric style with road and field crud. The cheapest appears to be the best for abuse.
Also, if you go to a big enough store you can get them keyed alike. I bought my first one at gunman's shop, and I found a matching lockset number in another store. One day I was at a big box hunting shop, and they had a large display. As I looked they had several that were keyed alike.