An open source re-implementation of RollerCoaster Tycoon 2. http://openrct2.website
syslog-ng is an enhanced log daemon, supporting a wide range of input and output methods: syslog, unstructured text, queueing, SQL & NoSQL. http://www.syslog-ng.org/
Redis is an in-memory database that persists on disk. The data model is key-value, but many different kind of values are supported: Strings, Lists, Sets, Sorted Sets, Hashes, HyperLogLogs, Bitmaps. http://redis.io
Parser combinators for binary formats, in C. Yes, in C. What? Don't look at me like that.