DEF CON CTF is something like a World Cup of all information security competitions. Our team blue-lotus have advanced to the finals for 3 years and I am selected to be a member of the finalist team for 3 times.
I was not very skilled at reverse engineering so I did more on assistance: system administration, binary hardening and various development.
System administration
I was charge of system administration of our gamebox and developed
many scripts during the contest: 
PCAP search engine
I built a PCAP/PCAPNG search engine with 2 people to make it easy to
analysis captured network frames. 
I wrote a compressed full-text string index based on FM-index which was the core of the PCAP search engine, the website backend and other stuff.
ELF
Userspace exec on i386, x86-64 and ARM.
Some binary hardening stuff.
Linux backdoor.