Mapudungun, the language of the Mapuche of modern south-central Chile and southwestern Argentina, did not have a writing system when the Spanish arrived.
There have been a number of proposals for orthographies or Mapudungun alphabets, all of them using Latin script, but no consensus has yet been achieved between authorities, linguists and Mapuche communities on the one to be used.
The main systems (in order of proposal) are the following: A more thorough look at the sounds of Mapudungun is available here.
Also, Raguileo aims to use only one grapheme for each phoneme (no digraphs) so it uses some letters from the alphabet in an unexpected way.
(*) /ʈʂ/, which is spelled "tr" is also pronounced [tɻ].