anything extra should be a REWARD. The word reward implies something given to encourage/thank players for doing well. A random system dose no such thing, it's all luck. And when something is determined by luck then it's no reward of skill at all.
That being said, things that actually affect game play should be open to everyone. Only cosmetic or "for fun" things should be rewards. For example, what if the top 10% of players got a over powered weapon. Then because of said over powered weapon no one could beat them. You end up in a "the rich get richer" situation where the older more experienced players get all the good stuff and new players can't, not due to inexperience but because of lack of said stuff.