GPICD - The GNU PIC Programmer and In-Circuit Debugger. GPICD is an open-source Programmer and In-Circuit debugger for the Microchip (TM) PIC (TM) family of microcontrollers. It is an ideal complement for the gputils development tool set.
PrivateICE is a kernel level debugger similar to SoftICE on Windows. Planned is also a GUI interface for normal debugging in a multitasking environment, as opposed to SoftICE which always halts the entire machine when active.
phook is a userspace tool which injects code into an application to make it do whatever you want. It has a modular design to allow users use different plugins. Default plugins are able to read and write into file descriptors belonging to another process.
playstation (psx) development tools: includes disassembler, code profiler, and cd mastering tools (split off from the World Foundry GDK).
The dude is a UNIX debugging package independent of the ptrace() system call; it consists of a kernel module [the_dude.o], a library to interface with the module [libduderino.so], and an ncurses client [ddbg] .
vMac is a free Open Source Macintosh emulator that is available for Linux/X-Windows, Win32, DOS, MacOS, and more.