Please read everything before attempting this glitch. I'm not completely sure if this has been posted in the past, but for the two maps that have radiation - Afghan, and Wasteland, you can glitch outside of the radiation fields and stay alive.
Steps:
1. Put: Tactical insertion, marathon, lightweight, and pain killer on a class (marathon is optional, but nice to have, you may want to just put one man army on)
2. Place an insertion within a couple feet of the radiation
3. Get killed BY AN ENEMY! Note - THIS IS THE ONLY WAY TO GET PAINKILLER!!
4. Place another insertion and repeat process until painkiller is obtained
5. Once painkiller is obtained, sprint out into the radiation, you absoloutely must have pain killer still on with 5 seconds when you start to get hurt or this won't work.
Other Notes: This will not work on hardcore because you have less health and you will die either way.