OpenBSD - Secure by Default
Provide safe configuration out of the box; see Theo's talk (Thursday 1:30)!
Total Code Audit: Multi-year, multi-national, ongoing
Integrated cryptography (kernel and userland)
Thorough documentation: man, faq
faq is at http://www.openbsd.org/faq/, and on the CD
Please learn to RTFM :-)