My longest ongoing boycott is Nestle. I've probably bought a Nestle product by accident at some point or another, but if I see the logo or know it's a sub brand it's a no go. My newest boycott is LTT/LMG (Linus Media Group).
I left Reddit but I'm not sure if I would qualify that as boycotting. I don't browse there but I still use the search terms for niche information like I did in the past. Reading this thread I see a lot of boycotts that I agree with, but I wouldn't qualify as my own since I'm not doing anything out of the ordinary. Take Hobby Lobby, I've never had cause to go there so I've never gone there. If I had cause to go there, I would find an alternative but it's not like I'm actively going out of my way like I do to ignore Nestle products.
I still get Chick-fil-A occasionally, it's one thing I feel guilty about. Not often mind you, like once every few months, but growing up I had fun memories there with people I won't be able to make new memories with, so I find it comforting.