Well, there are lots and lots of options out there, you have the MSAR AUG, the Israeli Tavor, the Remington ACR, and the list can keep going all day long. The two rifles I do suggest are the AR 15 and the AK 47. The reason being is that both weapons are superbly popular, easy to use, and capable of being excellent fighting weapons.
The reason being is that both weapons are superbly popular, easy to use, and capable of being excellent fighting weapons. AR 15s and AK 47s are so popular that there are tons of different options at varying and competitive prices. Aside from that there is tons and tons of aftermarket support for them. You can find magazines, accessories, ammo, upgrades, all very easily.
With so many clones and copies, and variations you can also find spare parts easily and cheaply, and they won’t be going anywhere anytime soon. For example, I mentioned the MSAR AUGS, which are great rifles. However MSAR is going out of business, so where will support come from, like spare parts when something breaks?