From my experience this is what I have seen/heard the Feebs ;) doing: Terrorism, Bank Robbery, white collar, some dope, run task forces.
ATF: Illegal firearm possession (Felons, drug users, etc), Firearm/Dope Trafficking and Possession, Arson, Explosive Possession/Bombing (after the explosion, not threats), Interstate/International Firearms Trafficking, alot of Search Warrants, surveillances, arrests, undercover, etc., related to the above areas of investigation, work on task forces, work WITH the local, state, and other federal authorities.
I can't say much for any other agency than my own, but the best place to check is all the different websites, they will have sections that go over all of this.
...We live in black and white, Your just a parasite, Now close your eyes and say good-night... Andrew WK