Sure. Accessing C FFI. Calling low level code like asm!, SIMD and so on.

You'll never be able to truly escape it, just mostly. -- One interesting suggestion by matthieum on Reddit was to make previously safe fn unsafe.

DMA, because the buffer can be linked to a designated RAM section, and it needs to be declared as a static mutable.

There would be many examples when code is running at lower levels with no OS abstraction

The 3rd paragraph has 3 bullet points about it.

There quite a few APIs which do not have safe wrappers. Recently I needed to disable IP fragmentation on a socket. I had to invoke the raw c library which is unsafe.