Such a list would be almost interminable. You could ask "what sorts of things is pure C still used for?" and then you could get a reply that lists categories - the GNU suite, drivers, kernels, etc. - but asking for a list of C programs is ridiculous.
As for the future of C in an age where more tasks are being done in parallel, the C11 standard may give better information than I can.
Ok, I ask to list by relevancy and popularity, like at least top 20?? Or at least list promising recent/upcomming projects.
Interesting projects could include Linux/PostgreSQL (current) and Redis (pretty new); I tend to steer clear of unmaintained software, so I cannot help you there.