While the OSS community converges to Git, with the Python bunch branching to Mercurial, the typical workplace is stuck with Subversion. The author's DVCS of choice is Fossil. These are all fine projects, with their own pros and cons, but what you usually want is just a tool to store your code tree snapshot in a safe place. They can all do that, but their language differs a tiny bit. repo brings them all down to the common root. It works by detecting which VCS are you using right now and calling that, applying necessary subcommand translation if needed.
retainCounter is an application that converts a simple [object release] into a NSLog(@"object retainCount: %i",[object retainCount]); [object release]; command. This is sometimes useful if developers wish to know the current count of an object before it is released, which makes it easier to detect memory leaks.
rioutil is a utility designed for the use of interfacing with Sonic Blue/dnna's third, fourth, and fifth generations of flash MP3 players (Rio 600/800/900/S-Series/Riot/Cali/Chiba/Fuse and Nike psa[play). On many players, it goes beyond the packaged software by providing downloading.
rlimit is a program that lets you run processes with system resource limits set. It can be used by software developers and testers to test that software will run correctly in resource restricted environments. It is also useful for software which would otherwise consume excessive resources such as programs that used 100% CPU, set their own priority levels, or consume too much memory. This is basically a command line interface to the system functions getrlimit() and setrlimit().