Halfling barbarians work out better than you might think. They get exceptional AC for light armor wearers (due to size and Dex bonus), and the barbarian class abilities compensate for a halfling's deficiencies in melee (low Str, low movement rate). Plus the halfling saving throw bonuses help offset the barbarian's poor Will save, and the racial skill bonuses are all in barbarian class skills. The newbie game I run has a halfling barbarian as their main tank, and he's managed just fine.