Just to humor you, things that can brick your Wii (not an exhaustive list mind you):
Downgraded IOS on a new Wii ("LU64+" Wiis)
Downgraded System Menu on new Wii ("LU64+" Wiis)
Corrupt/Missing System Menu on any Wii (this could happen if you try to reinstall or upgrade the System Menu through homebrew or with WADs and something goes wrong)
Corrupt/Missing System Menu IOS (this is an IOS with a number ending in 0. Again, could happen if you're reinstalling/patching the IOS and something goes wrong)
Malformed banners on channels (can happen if you're making/installing custom channels and they're made incorrectly or install incorrectly)
Installing an update from an out of region update
Installing a System Menu theme for wrong System Menu version, or install not working correctly
Deleting key System Titles with a tool like AnyTitle Deleter.
All apps on WiiBrew which have the potential to brick your Wii have a banner saying so on their wiki page. Check if the banner is there before using apps.
Games and emulators don't access NAND, so cannot brick you. Its really only apps which actually INSTALL stuff or MODIFY stuff on NAND which can harm your Wii if used incorretly or poorly coded.