A 9mm Glock is what I would prefer for a handgun (Glock 17 if you arent going to conceal) because they are simple and reliable.

However, some people don't like the grip angle of the Glocks. The Beretta 92FS is a good handgun, especially if it is well cared for. I'm not a huge fan of them personally, but they are reliable and well made.

AR-15's are great but the ammo costs would lead me to not recommend it quite as much. However, it is some of the cheapest rifle ammo out there, so not terrible. Just not as inexpensive as 9mm.