How acceptable/appropriate is the pronunciation of words such as "Christian" and "fortune"/"fortunate" with a [t] sound as opposed to [ʃ]? I personally prefer the former but I believe that it's not that common. Still, I'd like to hear what others have to say here.
/t/ is palatalized to /ʃ/ when it precedes the -ian and -ion suffixes. (Well, "Christian" has like two different pronunciations, depends on speaker), except when preceded by S, where it becomes /tʃ/.
/t/ is palatalized to /tʃ/ when it precedes the -ure suffix (e.g. nature), as well as in fortune and its derivatives.
In several American dialects (though not all) /t/ is often retracted to near /tʃ/ when preceding the R sound. (betrayal, nitrogen, try, train, Tracy, etc.)