For a rifle, I would say you should get a Ruger 10/22, in any of the number of setups. Lots of parts and addons for them. Also this is 50th anniversary 1964-2014. They are real easy to learn basic gunsmithing and do upgrades yourself.
I've been thinking on getting one, maybe once I get a job and save up the money I will. I'll probably just get a standard one and then Red Jacket Firearms makes a cool looking bullpup conversion kit. You could use it left or right handed and use the 25 round mags. Or the Archangel Nomad, it's just a conversion kit that'll make it look like the HK G36C assault rifle.