I have two favorites - one was from a company that made different flavors of powdered Chai tea (I think it’s called Big Train? It hasn’t been sold in stores where I live in well over 15 years - at least, I haven’t seen it!). The design is the one that’s featured on all of their packaging, and on the inside of the cup it says “Drink Chai. Embrace Life.”. Once, I told someone in my high-school class that I had that same mug upon showing them the photo, and they didn’t believe me so I brought it in the next day to show them. I don’t know why I’m so proud of having that mug, but I do really miss that chai.
The other is a mug that I painted myself at one of those pottery-painting places. It’s red and has the Team Magma logo from Pokemon, as well as the katakana (I think?) for the team name. It’s pretty decent for something I painted myself, if I may say so.
I do have an honorable mention that I got for Christmas last year - it’s a white mug with Mewtwo levitating a cup of coffee in front of him and “Brewtwo” underneath. It’s a smaller mug, but it shows that my brother-in-law knows me pretty well. lol