title_body: Is it possible to make a declension system that DOESN'T limit what nouns can end in? This has always been a conundrum for me. I like how grammatical case frees up word order, but hate how it puts a limit on what nouns can end in. Years ago someone told me of a natlang that uses 6 declensions, one for each vowel and the 6th for nouns that end in consonants. This allowed nouns to end in any phoneme in the language, though from my own research only plurals were allowed to end in -u. Sadly, I haven't been able to find that language again.
  
  Such a language, if it were to exist, would make it abnormally important to remember each noun's declension class, because what would be the nominative for one noun may be another case entirely for a different noun. 
  
  I find it annoying that I can't find that natlang again. I think it was a part of the Slavic family, but I'm not sure. I think it was spoken like somewhere around Eastern Europe or the Caucus mountains.
upvoted_answer: Ignoring the lost natlang, I'll just answer the title question:
  
  There are several possibilities to let nouns end in any phoneme of the language and still have case inflections:
  
  
  Most simple: Have a zero ending in the nominative singular
  Base your inflection on prefixes (like in Bantu languages) or infixes (like in Semitic languages)
  
  
  BTW, inflections with thematic vowels (like in Latin and Greek) aren't particularly difficult to remember, because the thematic vowel is easily recognisable throughout the whole inflection paradigm.
  
  PS Many natural languages have only a restricted set of allowed phonemes at the end of a word. Classical Greek is an extreme example of this kind of restriction, but also German has Auslautverhärtung aka final devoicing: Final consonants are always devoiced. This feature does not show up in writing but only in the spoken language.