I think I'll include anything here that might be considered B, C, or Z movies, as well as parodies of/homages to the genre. Though technically, B-movies aren't a "genre"; there are actually lots of different genres that can be B-movies, including but not limited to:
action/adventure, badass, classic horror, giant monsters, martial arts, scary, sci-fi, supernatural, weird, and westerns, etc.
However, I don't always know whether a movie technically qualifies as a B-movie or not. I'll do my best to figure out what to list here, but you'll probably find some movies listed in the above categories that I should include in this category, but don't. (On the other hand, there may be some movies I do list here that aficionados wouldn't consider B-movies.) Anyway, I should say that, in theory, I like the idea of watching B-movies ironically or to make fun of them (a la MST3K), but in practice, I have little interest in such things. And even when I do manage to enjoy such movies, I still can't enjoy them with the same level of cultish devotion that serious B-movie fans do. (Though there will also be some B-movies that I really enjoy un-ironically... more or less.)
Here are some links to sites or lists that know more about the subject than I do:
10 Modern Day B Movies You Need to Watch (IFC)
The 100 Best "B Movies" of All Time (Paste Magazine)
B-Movie Central (this site is gone)
The Best B Movies of All Time (Ranker)
Lost Highway (this site is gone)
Most Popular "B Movie" Horror Titles (IMDb)
Oh, and incidentally, I want to mention something else. One night, probably in the mid-to-late 80s, I was watching a movie on TV (looked like it was probably made in the 70s). I have always considered it the worst movie I've ever seen, but I have no idea what the title was. In the years since then, I have occasionally done web searches, trying to figure out what it was, but I've always failed. So here's what I can tell you: This young man returned to his home town after being away (at college, or after having moved away for work or something). There are mysterious deaths in town, which no one could figure out, but it seemed obvious to me throughout the movie that inanimate objects (or more specifically, power tools and electrical appliances) were, for some reason, coming to life and killing people. It's not like we ever saw this shown explicitly, it's just the impression I remember having. The kind of thing that's so obvious to anyone watching a movie, that you can't understand how the characters can't figure it out (except that from their perspective, they're living in real life, not a movie, and things like that don't happen in real life). But at the end of the movie... well, I don't want to spoil what happens. But if anyone has any idea what this movie might be, please let me know.