G-WAN sparked some controversy within the Phoronix Forums since the G-WAN developers claim that their server is the fastest and holds a unique feature set, but it's all closed-source albeit it's free as in beer. Gatling also claims to be a high-performance web-server, but it on the other hand is open-source via their CVS repository.
Gatling claims to be a 125k static Linux x86 binary with HTTP/FTP/SMP support, very fast, scalable, platform-specific performance and scalability APIs on multiple platforms (Linux, NetBSD, FreeBSD, OpenBSD, Solaris, AIX, IRIX, Mac OS X, HP-UX), IPv6 support, transparent content negotiation, FTP upload support, cheap htaccess support, and various other features. Gatling also has a wish-list work item of NFS support.
There aren't any Phoronix benchmarks to test these high-performance web-server claims, but some may be conducted in the near future. For those wanting to learn more about Gatling, visit its German web-site.