Just 1k? Drugs are probably the best option. Buy in bulk and flip for profit.
Honestly flipping drugs is generally a bad/high-risk idea but at a one time investment of 1k it might be a pretty solid option. Really depends on your connections and your intended market. I know that I could buy 1k of acid from a friend of a friend and I could sell out in a week selling only to people I know at a college that doesn't usually involve police in drug matters. I would be way too paranoid to try to sell to strangers who might rob me or deal on the street where cops could pick me up.
Don't try to flip a car if you don't know shit about cars.
You could also try buying some bluechip stocks the next time the market dips like it did last month when there was all that FUD about Greece. I would hold them for a year rather than try to sell them off quickly (for tax purposes as well as general investment philosophy).
If you planned on regularly contributing $1000 to an investment account, let's say, then it would be a good idea to invest in index funds and hold them long term (as in, decades). Since you're on this forum you're probably not interested in retirement or long-term financial planning, but this is the smartest way to invest your money.