If you skill up in the Stack API, what purpose does it serve? What can you do with the API, how can you apply it in real world scenarios?
There were a couple of old questions on Meta that had a lot of good ideas.
What do you want to build with the SO API?
What would you want to see in a StackOverflow API?
For some examples, look at the postings under the apps and library tags.
You can write applications that leverage the so body of content.
There is a whole 'apps' tab full of 'real-world' examples.