First I'll say this, there's no such thing as an assault rifle. Any firearm can be used to assault people, assault rifle was a media coined termed to make them sound serious and scary. The only rifle that can be even considered an assault rifle is the sturmgewehr 44, because it's name means "storm/attack rifle". The rest are semi-automatic, or automatic rifles or carbines. And to answer the question, I'd take an FN-FAL semi-automatic rifle. It's accurate, powerful, and semi-auto is far better in any circumstance aside from providing covering fire. The added bonus is that it almost never jams, unlike M-16 and M-4's, and the AK-47 can't provide nearly accurate enough shots to protect anyone.