Orange Lightning
Purple Belt
The arch or kind of the middle of the foot for some stop kicks generally. Used as a block. And the oblique kick.
I side kick with the heel.
There are some weird variations. Pointera in capoeira is done with the toes.
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Somebody on this site posted a link a while ago about really old karate kicks using the toe. Apparently for striking the nerves. The article I read said some "karate expert" once toe kicked a guy in the armpit, and it killed him somehow.
Not the same article, but here's another.
The Old Okinawan Karate Toe Kick karate2sentena4