Could you tell me what's the best pain killer for toothache?

The one that works: I don't mean to be sarcastic or facetious, but different pain medications work differently for individuals. There is no "one" best pain medication. One more important point- pain medication only covers up the pain temporarily! you need to have the cause of the pain determined and treated. Only a dentist can do that. Call right away!

Dental treatment: Otc pain meds only mask the symptoms. If you have a toothache, almost assuredly you have an infected tooth. Don't wait, it will not cure itself, call a dentist for an emergency appointment before you have severe pain and before the infection spreads. There are no substitutes...Call a dentist, now!