Index funds are statistically the best option. With index funds you own a piece of almost everything.

To quote Warren Buffett:

My advice to the trustee couldn't be more simple: Put 10% of the cash in short-term government bonds and 90% in a very low-cost S&P 500 index fund. (I suggest Vanguard's.) I believe the trust's long-term results from this policy will be superior to those attained by most investors — whether pension funds, institutions or individuals — who employ high-fee managers.

http://marketwatch.com/story/warren-buffett-to-heirs-put-my-estate-in-index-funds-2014-03-13

I found the Warren Buffett article and quote on investing in this Reddit thread:

https://reddit.com/r/personalfinance/comments/4nnt2c/i_have_1000_to_invest_i

Cross posted to Imzy:

https://imzy.com/personalfinance/post/warren_buffett_on_where_is_best_to_invest