(warning: mild coarse language)
One recurring issue of pronunciation for many learners of English as a second language is making the difference between /i:/ (long ‘ee’) and /ɪ/ (short ‘i‘). Many languages have one high front vowel, which is usually /i:/ but which can turn into /ɪ/ without turning into a different word. (Technically, in English /i:/ and /ɪ/ are phonemes; they make different words. In many languages they are allophones; they are simply a different pronunciation of the same word.)
One famous book on English pronunciation is Ship or Sheep? Many other pairs of words illustrate the same phonemic difference. In my Korean diary, I noted: ‘Another class was talking about risk and adventure v calm and security and one student said “Since I know Jesus, I have piss in my heart”.’
In Australia, one student said that he was talking to his boss on his mobile phone while on the train. His boss asked if he’d seen the new work schedule. He replied: ‘Yes boss, I see ze shit in ze kitchen’. He then said to us: ‘I finish ze phone call and see ze woman opposite me in ze train looking at me very strangely.’
Some time later I told another class this story in the context of a pronunciation lesson. I wanted them to bring the pronunciation worksheet with them the next day, so I say: ‘Please bring your sheet with you tomorrow.’ One student guffawed and I said: ‘I said “sheeeet”!’
Another student was talking about ‘a memorable day with friends’. He or she said: ‘I went to the bitch with my friends. It was a beautiful bitch. We lit a fire on the bitch. We ate our lunch on the bitch (etc)’. (Not to be confused with the movie with Leonardo di Caprio.)
In these examples (involving students from four different countries), it just so happens that /i:/ has been made as (or heard as) /ɪ/. Other speakers of English as a second languages from other countries make the opposite switch. To be fair, English speakers speaking other languages equally often fail to make the distinctions required by those languages. Korean has two mid-front vowels (에 /e/ and 애 /ɛ/), whereas English only has one, which some people pronounce higher as /e/ and some lower as /ɛ/. When I’m speaking Korean (which is rarely), I’m aware that there is meant to be a difference, but it’s probably a matter of guesswork as to whether I produce the right sound. I’m unaware of any minimal pairs which depend on the difference, especially it one of them is a rude word. A lot depends on context. If someone says ‘I have piss in my heart’, the meaning is clear, but their might be cases of genuine ambiguity: ‘Someone gave me a little ship/sheep for Christmas’.