Go to Port Royal. Go to Fort Charles, then go to the hanging station. Attack the level 14 to 18 grunt, and it will not retaliate as long as you are on the platform. If you step off the platform, he will start to attack and get veterans to help.Easy grenade experience
Go to Misty Mire in Tortuga, and attack the giant crabs, big alligators, and huge alligators using only grenades. They will not attack back.