I don't personally do this, but many people in my family say the days of the week with "dee". Like "Sundee", "Mondee". I think it's charming, but one of their children said they were weird for saying it that way.

Also, as a programmer, there are some words that programmers use that are abbreviated which I refuse to pronounce the way that others pronounce them because I think it's weird, but virtually everybody pronounces them different to me.

For example, there is a common keyword in programming languages called "enum", and most people I know pronounce it as "EE-num", like it rhymes with "ME dumb". But "enum" is short for "enumeration", so I pronounce it as if it's the first two syllables of "enumeration", like "ee-NUUM". Although I think the normal pronunciation is weird, I don't say anything to people. I just pronounce it the way that I think it should be pronounced. But on multiple occasions, other programmers have called me out for it and asked why I pronounce it "wrong".

There are several other programming terms like this, but they don't immediately come to mind. Enum is the most common example.