Play with a friend in Hardcore mode. Become a medic. When in a safe location, intentionally kill your partner then revive them with the defibrillator. Each time this is done you will gain get 80 experience points but also lose 15 experience points for team killing. Repeat this as many times as desired. Note: This can be also be done in an area where you are notified that you are leaving the combat zone. Have the other player walk out there. When they die, run in and use the defibrillator paddles to revive them to gain the experience points without the team killing penalty.