How to invest in expensive oil?

While most of you still don't think it's a good idea, or will work as intended, for me to go long on oil in the hopes that my luck will bring prices down ... I still want to know the best way to do it in the case that I later decide that I want to.

First, the constraints:

I have a Scottrade (brokerage) account, which lets me buy stocks (including ETFs) and bonds. It is not, however, authorized to trade in options (or futures or forwards or shortselling), which would take a few weeks to authorize (I have to send in signed paperwork). So the first, question is, should I go ahead and authorize that, just to be ready?

As for money, the account has about $3200 in an ETF (ticker PRFZ) and under $100 in cash currently. I can add to it from cash reserves or liquidating other investments (including the PRFZ). You can safely assume I can buy $10,000 worth of securities.

Next, I would like to keep this simple, so I only want to invest in only one security -- so nothing like "buy this one and short this other ...". (It is of course acceptable to suggest a single security that *itself* employs such a strategy.) I want the best one stock whose returns track the standard quoted price of a barrel of oil, and yes, that means include any dividends, which makes it that harder to look up with the free investment tools available.

So, the question: which security to buy? An energy sector equity ETF? A natural resources sector equity ETF? A commodities index ETF? An ETF that employs some leveraged strategy that amplifies size of oil price movements? The bonds of an oil-rich developing country? Or, take the plunge and authorize buying calls on oil?

Suggestions are welcome!