Note that an emergency may not necessarily be an extensional crisis; an emergency can simply be a need to take advantage of an opportunity.
I'd suggest paying off some debt, if you have any.
Also, if you have any debt at all (school loans, etc.) you can probably make a better percentage profit paying your debt off early than you can in any other way.
Even if you have an understanding of a sector, most people are horrible investors and a simple index fund will out-perform them.
Paying off a 5% interest debt gives a guaranteed return.
Sounds like you're the perfect candidate for the next Bernie Madoff... he guaranteed future returns of >10% on his mutual funds :-)
That said, a (heavily conditioned) case can be made for investing before paying off loans, as I did in my original comment for this thread.)
If you have the know-how, you can probably make a bit off sports betting, or stock investments, but otherwise high interest savings or a managed fund / superannuation would probably be best.
Higher return? Lower risk? Long or short term?
You can buy a lot of books with that and it could be (if you read it) the "best" investment.