Tactical Nuke

The Tactical Nuke is an unlockable kill streak in Call of Duty: Modern Warfare 2. Requiring 25 consecutive kills, this kill streak is the hardest to acquire in Call of Duty: Modern Warfare 2. Once used, a ten second countdown will be displayed for all players. Once the countdown expires, the entire battlefield will be engulfed in bright light, then gameplay will go into slow-motion and then every player will die (including the user), and game will end. If the user's team is losing when the nuke is summoned, the match will result in a win. The Toxic title can be earned by being killed by it unless you are respawning while it goes off.

Trivia

 * There is no way to stop a Tactical Nuke, even with an EMP. Proven here.
 * The nuke only kills players, not any sort of geometry on the map.
 * It's not impossible to obtain this from a Care Package/Emergency Airdrop, just very unlikely (Ref Robert Bowling).