[tobylane]

Bugs and symbols. There's a mac command line tool I can't remember the name of that pulls all the readable (and more) text from an application, this has been used to find out what made a closed source app (e.g. private iOS apis).

[blcArmadillo]

Is it maybe the strings utility: https://linux.die.net/man/1/strings?

[rl1987]

There's also nm(1) and objdump(1).

[istumbler]

There are also tools which are platform specific. On macOS, for e.g., the Mach-O format can be disassembled by `otool`, for objective-c projects (and maybe Swift) you can use `class-dump`