Investing in oil... Something that absolutely has potential as everyone needs oil either for cooking, for transportation and even just for lubrication.

Medical equipment is absolutely useful as well. I should know as a Pharmacist who works in a place that sells medical devices.

However, the next question is what medical device and what need will it fill?

Some very good medical devices still fail because of lack of marketing or patients not seeing that the price justifies the benefit. Or simply because the role they fill it too small to produce a profit for the providers.

As an investor I'd be curious to see what device, what need, and what market.