These are the top 3 most irritating grammer issues, for me anyway.
3. Their, there, they’re. One is possesive, one is an adverb (as my friend the Queen tells me, not a preposition), the last is the conjunction of they are. These are different words used in specific instances. Different instances.
2. Had Went. You may have gone, perhaps you went, but never ever will you had went anywhere.
1. Your & You’re. Again, one is possesive, one is the conjuntion of you are.
Feel free to add.