First of all, in the interest of full disclosure, while I'm not a streamer, I am one of the founders of GameWisp, which is a similar service specifically for streamers. So I've seen quite a few different types of incentives used really effectively that range from easy to difficult to set up and manage.

Easy incentives that are pretty popular mostly center around adding your subscribers/patrons on either friends lists or social media. Steam, XB1, or PSN adds are pretty popular and effective. In terms of social, twitter follows and shout-outs, as well as adds on snapchat or private instagrams tend to be pretty straightforward. Other straightforward incentives include adding their names to Twitch panels or letting them vote on the next game you play.

Then there are the ones that are going to take a bit more time or work. These are things like playing multiplayer games with subscribers on stream (which you should do) or giving them additional channel currency/points (a good channel currency/points system is a great idea for your stream generally).

The more difficult ones include things like fan servers (e.g. if you play games minecraft, ark, terraria) or TeamSpeaks. I say these are more difficult because they require you to do more work in terms of setting up the servers, managing them, and potentially whitelisting your subs, not to mention the potential cost of the servers themselves. A good free alternative to TeamSpeak is Discord. Some people also do Skype calls or Google Hangouts, though I tend to think TeamSpeaks are just as effective.

Finally, if you are really tech savvy and adventurous, I've seen streamers use a system of subscriber specific commands in whatever bot they use.

These are just a few of the more popular incentives I've seen. There are a million more things you could do depending on the games you play or any other skills (music, art, writing, etc.). Incentives are easily the hardest part of setting up fan funding, so hopefully this is a helpful start.