"Would of" and "I could care less" are probably the worst ones for me.

When people don't understand the difference between "Your" and "You're."
An example of what I see all the time would be, "You're ice cream tastes delicious!" (This doesn't make any sense.)
I also don't like it when people decide not to ever even try capitalizing anything.

Other than those, I could care less.

Another one of mine along these lines is "payed". I understand why people make the mistake (when they're 7 years old or so or a non-native speaker) but, we are on freakin' computers! We have spell check built into most of our browsers!

The game releases on Friday.

*shudder*

to release is a transitive verb!
The game is released on Friday, dammit! >:(

Other than that the usual:

affect <-> effect

should of, could of (ouch, just reading it hurts...)

I'm a translator and as part of my work correct orthopgraphy is essential. So even unconsciously I look for spelling errors...

- Confusing "apart" and "a part"
- "a whole nother"
- Using big words when it"s not necessary.
- Making long posts when it's not necessary.
- Refusing to use capital letters (bananaking)
- Confusing lifetime sales with LTD sales.
- Using an incorrect definition of "atheism"

You never know, maybe their purposes are very intense.

Your jumping to conclusions, could of meant something else.

I hate you.

All of them honestly. If English isn't your first language, then I'm fine with you making mistakes as you're learning and it's not that hard to work out what you're saying, but if you're a native English speaker then mistakes like your/you're, could of/should of, their/they're/there, etc. are going to make me want to throttle you. I like language and plan on becoming a translator, so I hate it when people mangle a perfectly good language so that they don't have to type a few extra letters. Is it seriously that hard to type could instead of cud or love instead of luv? >.>

This. Exactly this. I was entering the thread with the intention of having this rant but you put it here beautifully. I can't even describe how incensed reading this makes me. Maybe I should get a life...