Bsnes+

This tool is VERY useful, especially when creating huge ASM projects:

-crashes from using invalid register size. This is common when you are using both 8 and 16-bit together around the code.

-When using layer3 status bar/Overworld border patches (SSB, Minimalist, SMB3, OWB+), this debugger have S-PPU tilemap viewer that enables you to find a coordinate of a given tile (position x,y), without having the user to manually guess or take a screenshot and count every 8th pixel to find what tile to modify what corresponds to what address. I've made an HTML for those patches that makes this even easier.

Even the ASM tutorial made by Ersanio recommends this tool.

Also, even better, use Asar's print command (print "brief description of the RAM:", hex(!Freeram+$xx), so you'll know what RAM address it is to compare the RAM it uses in the debugger).

Replaced my default emulator + debugger with this and been using it the last couple weeks for various dev work and Crowd Control development. Debugger additions and normal emulation all seem to be working well.