I'd go for a military bolt rifle if I could only have one. preferably a mauser 98k, or SMLE. I'm not a fan of mosins, but I wouldn't complain about having one.
They're good at distance, good for hunting, and are built like clubs. they also have spikey attachments, and with practice will do nicely for things that are close, or rather, too close.
Imagine what I would do, if I could do all I can.