What painkillers are good for forearm fractures?

Depends: This depends on a number of factors such as the type of fracture, whether surgery was done or not, and, possibly most importantly, the pain tolerance of the individual. Essentially all painkillers are narcotics (other than tramadol), and most physicians will start with less potent painkillers and increase the potency as indicated.

NSAIDs: After rest (immobilization), ice, compression (by cast/splint), and elevation, the next best treatment is a non-steroidal anti-inflammatory drug like ibuprofen. This class of medication helps with swelling and pain. Although narcotics can help with break through pain, they do not assist with swelling which is the typical cause of pain, and of course, addictive with prolonged use or abuse.