I don't know if decompilers are able to do something about it, but there's a "neat" technique where your machine code can be interpreted as two different sequences of instructions depending where you start instruction decoding. For a simple but artificial example of what I mean:

The following sequence of bytes:

  b8 50 83 ec 10

Decodes as:

  mov $0x10ec8350, %eax

if you start at the first byte, and, if you start at the second byte, as:

  push %eax
  sub $0x10, %esp

Here I essentially hid an instruction in the mov'ed data, because that's the easiest way to create something like that, but I've seen mind blowing examples of this technique. I unfortunately don't remember where.