The only other one I can think of is kind of poor ergonomics around "self-borrows"; it's a lot less common than I've felt the need to mutably borrow two fields from the same struct independently, but there have very occasionally been times where I've realized the simplest way to structure something would be to have one field in a struct borrow another. This is somewhat hard to express given the need to initialize all of the values of a struct at once, and even if you could, there are some complications in how you could use such a struct (e.g. not being able to mutate field `a` safely if it's borrowed by field `b`). Overall though, the things that Rust prevents me from handling safely because of its own limitations rather than them being fundamentally unsafe are quite rare, and even with those, they tend to be things that I would be quite likely to mess up in practice if I tried to do them in a language without the same safety rails.