I settled on TCLAP after scouting for a while for a command line parser. It's simple to use, gave no warnings on gcc/msbuild under fairly strict options. I found it convenient to provide arg values by reference and I removed the traits bits to cut the boiler plate even further and shrink the amount of code to suit my taste. It speaks well of TCLAP design and implementation that I could make those changes in a very straightforward way.
Really nice, easy to use and extensible command line interface. I like the header-only-ness.
I've used this library for almost 10 years. It compiles warning-free under g++ using "-Wall -Weffc++ -pedantic -std=c++0x". It keeps parsing simple, allows for parameter ranges, and exclusive-OR argument specification.
This is an excellent C++ library for command line argument parsing. Quite simply the best I have ever seen and I've seen quite a few.
Good Stuff! Makes command line parsing pretty simple.