A bunch of them. I might have about 60 GC games. Some of them are not booting but instead of the black screen it switch off the console, must be just bad injects.
Starting a game without the SD, usually gives you a "boot.dol missing", but in these cases not it shutdown the WiiU without launching Nintendont. Might just be a bad iso.
But beside of that all GC classics are booting with no issue.
Make sure your isos are clean first. Use md5Checker tool to compare the md5 hash of your games to the ones found at redump.org. If you happen to download your isos from... somewhere, make sure they are clean before injecting them.
I'd also advise you to make your own iso backups if you can, using cleanrip on a modded wii is very simple. It's what I've used to rip my entire set of GC games.
I've only use Teconmoon's injector with no problems so far. Keep it mind it does not work with CISOs files (I haven't managed to do so at least), so using clean, not scrubbed, not trimmed, 1/1 image files is your best bet.
It got a new update just days ago. Thanks to the work of dear lad @GaryOderNichts being merged by wonderful sir @pedro702, HID devices being plugged in don't crash the system on startup anymoreI don't know much about this issue as I just use a nintendont forwarder with my games, but the issue seems to be related to the latest version of nintendont. don't download it overwrite it like it might have you do with the forwarder app.