Somethings I remember generating a lot of excitement at first.
Mining, when it could still be done with graphics cards and early mining machines.
Gambling, the early sites SatoshiDice and later Just-Dice had huge followings. Looks like there is still a lot of crypto gambling just split up over many more sites now.
The early Altcoins such as Dogecoin and Huntercoin.
Tokens and Dapps made possible with Ethereum.
Earlier Tokens with the airdrops were very profitable.
Dapps looked very promising at first, not sure they've lived up to it yet.
What do you think is next?
I guess the next big thing will be the those large financial institution like paypal supporting bitcoin. I know many people hates the fact that PayPal supports bitcoin in a weird way where you don't actually own the bitcoin, have no access to your wallet address and cannot transfer your bitcoins to any external wallets. But they did say "for now" it is going to be like this. So we can expect things to change in the future. They are probably looking for a better way to allow users to hold bitcoins and transfer them to external wallets.
So, yeah the next big thing maybe banks accepting and supporting bitcoin? I know it sounds shitty since it is going to be all centralized and strictly regulated, but if bitcoin goes mainstream, the regulation is inevitable.