rp++ is a full-cpp written tool that aims to find ROP sequences in PE/Elf/Mach-O x86/x64 binaries. It is open-source and has been tested on several OS: Debian / Windows 7 / FreeBSD / Mac OSX Lion (10.7.3). Moreover, it is x64 compatible. I almost forgot, it handles Intel and AT&T syntax (beloved BeaEngine). By the way, the tool is a standalone executable.