title_body: What language uses the most amount of phonemes? I'm constructing an auxlang/artlang (temporarily named Syn). 
  
  
  
  The Syn is (being) designed to interface with any known human language, with a wildly uniform set of simplistic, unambiguous symbols.
  
  
  
  I have almost finished the phonetic alphabet component and have been trying to transliterate several languages into this while translating some that I know now on the side. However, since I'm not a native speaker of any of the transliterations and google translate is becoming not much of a help, I can't pinpoint the exact phonetic equivalent of some words. Now I'm running out of practice scripts from different spoken languages to accurately transliterate. Hence, I think I'm gonna need another language similar to what I'm making.
  
  
  
  Are there any languages, written or spoken, natural or constructed, that occupy majority of the entire phonetic alphabet, with as little diacritics, as few ambiguous strokes, and as strict 1-to-1 symbol-phoneme as possible?
upvoted_answer: You're gonna have a hard time with "majority of the entire IPA". Non-pulmonic consonants are rare, and some consonants are hard to contrast (e.g. /β/ vs. /v/), while vowels are often highly allophonic. Natural languages tend to have fewer IPA places and distinction via aspiration, labialization, etc.  
  
  My best answer to your question would be Ithkuil (constructed, almost unspeakable language). It has 58 phonemes, with unusually many vowels (13). This allows it to have mostly single phonemes for morphemes. Ithkuil's Roman transliteration is a bit strange, as some phonemes use diacritics and others have digraphs, but it also has its own script (morpho-phonemic with alphabetic characters).