Children's albums that go through davening and have the wrong dikduk. Girsa d'yankusa is real and it's much harder to correct later on in life.
Some easy examples:
There should be a pause between chemla and rabba emunasecha
It's v'ahavtA not v'ahAvta
+1
Also drives me crazy when songs quote pesukim but mangle the word order. I'm okay with words being repeated in order, but not when you say the words backwards for fun or repeat a phrase after words that come after it.
Same reason - you hear the song that way, you (or your kids) are apt to say it wrong.
Interestingly, my grandfather A"H apparently corrected a few songs and zemiros to be more correct in dikduk and to avoid word repetition when the zemer included Hashem's name. I only found this out later when I heard others singing them the normal way. So I guess this peeve runs in the family.