You beat me to it with the Glock 20. I think this is one of the most versatile handguns ever. With a red dot sight, detachable stock and multiple barrels in .40, 9mm and 10mm, you can't go wrong.
PTR91 .308. Basically the HK91. Ultra reliable and accurate. Magazines are cheap.
And the Kel-tec PMR30 .22 mag. 30 rounds, and the .22 mag is very underrated. I love it.