Ballistic: Ecks vs. Sever (2002)

Your most dangerous enemies are the friends you've double-crossed.

Jeremiah Ecks, an FBI agent, realizes that he must join with his lifelong enemy, Agent Sever, a rogue DIA agent with whom he is in mortal combat, in order to defeat a common enemy. That enemy has developed a "micro-device" that can be injected into victims in order to kill them at will.