1. Beer - I drink more of it than I should, but I love it.
2. Work Lunches - I don't bring lunch from home nearly as much as I'd like to (100% of the time is my ideal), because I'm on the move a lot and there's no guarantee I'll be able to actually eat the lunch I brought; I've had to throw out several lunches I never got a chance to eat. Luckily, lunch is paid for by my company when I have to work through it, and this happens pretty frequently.
3. Musical Equipment - They're considered luxury products, but making music is what makes life worth living for me.
I will say that when it comes to these three superfluous expenses, I still practice frugality. I drink cheap beer and I rarely go to a bar. I buy work lunches that cost $5-8 whereas my coworkers will routinely spend $12 or more on their lunches. Almost all of the music equipment I buy is used, I do a lot of research to make sure it's something that will hold value, and I sell things when they're no longer useful to me (I've even made a profit off of some of it this way).
So I try not to beat myself up too much about it, even though there is plenty of savings to be had if I managed to cut out these things entirely. I count myself very fortunate that I don't care about clothes, tech, furniture, cars, glamorous vacations, and other lifestyle signifiers.