The three language misuses that irk me the most are three VERY common mispronunciations:
1. Mischievous -- It is NOT mis-chee-vee-us!
2. Often -- It's OFF-uhn, not OFF-tuhn!
3. Sophomore -- The middle "o" is silent!
MM
So, does one attend an orientation to be orientated?
Among my pet peeves (mostly involving incorrect pronunciation):
ek-specially (especially)
deth (deaf)
nethermind (never mind)
stoled (stole)
ax (ask)
probaly (probably)
renember (remember)