I came up with a crude debugging trick today. Suppose an interesting number is in rax at a particular point in the code, then insert these lines:
add rax, 0x41000000
call rax
You now see a crash at for example RIP=0x000000004100000C in the debug board and know that rax was 0xC == 12 at the time of the artificial crash. The add instruction avoids accidentally jumping into real code or data.

This can of course not replace a proper debugger.