What if you invest in yourself ? Or a business you know ? Bitcoin investments dont really exist because bitcoin is so volatile I guess.
You can count altcoins as investments too. Gambling is much better then HYIP though.
First, lets define "Bitcoin investments". In my mind it means "giving your bitcoins to someone with intent of getting more bitcoins later". There are many scams that offer this type of deal - hyips, cloud mining, ponzi schemes, scammy ICO's, etc. But there are also legit ways of investing - casino bankrolls and trading for example. But there's more! Here's the board called "Securities":
https://bitcointalk.org/index.php?board=78.0There are many different opportunities for investing there, and some of them are scams, so you should be very-very careful and never invest more than you can afford to lose.