You have some variations on the theme of assembly, most notable being HLA
http://www.plantation-productions.com/Webster/ which includes a lot of premade stuff you can use. Depending upon how you want to view it then return oriented programming is another type of low level assembly ish programming.
Equally what counts as low and high level is up for debate -- some would classify C as a low level language and save high level stuff for things with interpreters (java, javascript, python, perl. lua......).
Where are you looking to go with this? The question itself does not mean the most but if you want something fast then we can do that or if you want something you can use to pull things apart... well you are still going to want assembly but there is still stuff we can link beyond that.