Not so much a pet peeve, but something that's often hard to remember.
Effect and affect:
Affect is always a verb and means to bring on our cause a change or to cause emotion or provoke feelings.
Example: The law banning minors from voting no longer affects me because I am over 18.
Example 2: The movie "Dead man walking" affected me deeply.
Effect can be used as a noun or a verb. As a noun, it means the result.
Example: The effects of the earthquake were devastating.
As a verb, it means to accomplish or bring about.
Example: If you want to effect a change in the policy, you must write a letter to the council.
Why do we play with fire?
Why do we run our fingers through the flame?
Why do we leave our hands on the stove, although we know we're in for some pain?
-tick...tick...BOOM!