why would you choose a spear? they're big and awkward and you only have one chance to hit your target, within like what? 30 yards or so? unless you're freaking zeus or something that ain't happening
a compact bow would be a much better idea. better accuracy, more chances, faster, not awkward, i mean come on.
carry a knife for when a guy is up in your grill also. you get better control and accuracy with a knife than with a knife on a stick.
That said, I would say a good camping/hunting knife. You know, the ones where the bottom screws out and there's like a needle and thread and random stuff.