Another one in the theme: Fishing line or nylon string. A transparent fishing line can hang pretty much everything and supports 10kg or more.

Need to cut a cake into top and bottom halves? Fishing line can do that too. Do a hitman choke thingy around the cake.

Keychain? Can be done, why not.

Nail is too far to hang stuff? Just tie a fishing line between the things

Cracked plastic needs extra support? Fishing line.

Out of zip ties? Fishing line.