Ask HN: What kind of hackathon do you like?

We (hackerrank.com) are planning to visit a few schools (Harvard, Princeton, UFL, etc.) in the next few weeks to conduct a hackathon. I'm not a big fan of "Here's our API, lets build something cool" type because students might be tired of every hackathon being the same type and there a number of them that happen every month.

There are other ideas we have in mind like a bot-vs-bot contest. What kind of contest would you like?