Pretty much anything with “automagic” properties, anything based on proprietary “cloud”, or anything so big I couldn’t possibly audit it (not saying I audit everything I use, I just want the ability). Oh, and also, products claiming to be “security oriented” when they are, in fact, not.

I sometimes make exceptions for “least terrible in class” when I absolutely have to use a given software or be irremediably cut off from a big part of society, like with AOSP and Signal. But those exceptions are few and far between, so there isn’t a lot of popular software I use.