MacsBug also had a ton of MacOS-specific features, like transparent integration with the 68k emulator, the ability to display symbols for both application code

MacsBug also had a ton of MacOS-specific features, like transparent integration with the 68k emulator, the ability to display symbols for both application code and the system ROM, and a wide variety of tools for interacting with the Memory Manager and Resource Manager (including intrusive operations like compacting or purging memory). It also had mouse support -- you could click any address on screen to view its contents and information about the memory region it was in, for instance -- and a menubar. :) Macsbug won't run in the SheepShaver emulator, as it takes a number of shortcuts which are incompatible with MacsBug. It works fine under qemu-system-ppc, though!