Common & uncommon soap ingredients

[NatureandNurture]

So I know most of the common ingredients for soap (oils, herbs, etc). And some of the lesser known ones too (honey, beer, milk, etc). But what are some really off-the-wall things you've added to soap?

 

[krissy]

tree sap.
i dunno if that is common or not, lol

 

[Artephius]

I did a coke soap. I've seen references to 7-up & Irn Bru as well. (all sodas)