I would say either Science or English, although for the latter, whether or not it is actually good or fun depends on the teacher and how they go through the subject and the texts you read. As someone who enjoys debates and writing, I’ve enjoyed English class when we talk about the story and ideas presented in the texts we read, and I even enjoy writing essays when I find the topic especially interesting. Again, though, this is dependent on the teacher.
Science, on the other hand, is almost always interesting and fun, especially when it involves experiments/lab work, whether it’s Physics, Biology (dissections and whatnot), or my personal favorite, Chemistry. Now, that’s not to say a teacher can’t ruin this subject as well, but that’s a bit harder to do than it is with English,