Some expressions I detest or find often misused:

1) "Life is too short" Oh, is it?

2) "I could care less" when it properly should be "I couldn't care less" since saying "I could care less" implies you care somewhat.

3) People who write "That being said," when the "being" is superfluous. It's properly said: "That said,"

4) "my bad"

5) "long time no see"

6) "ya know what I'm sayin'?"

7) "multi-tasking"

8) "prioritizing" (prioritising?)