No federal agency has unlimited jurisdiction.
Added: The above answer, as a 'blanket' response to the question, may be correct.
HOWEVER - There ARE certain federal law enforcement agencies whose jurisdictions ARE unlimited when pertaining to specifc federal crimes. The question needs to be clarified or limited to a specific area.
FBI
Added: Actually there are many such law enforcement organizations within the Federal Government which have so-called "unlimited jurisdiction" and to the above can be added;
the US Marshall's Service - Immigrations and Customs Enforcement - US Secret Service - The Bureau of Alcohol Tobacco and Firearms - The US Park Police - The Executive Protective Service - and probably several more which escape me at the moment.
They are ALL Federal Officers and all have nationwide jurisdiction.
While their primary mission may be the enforcement of select laws and regulations they are lawfully empowered to make arrests for ANY violation of federal law ANYWHERE within the US.
Federal Aviation Administration (FAA)
The FBI is a Federal law enforcement agency responsible for security and law enforcement in the United States.
Federal Aviation Administration (FAA)
the answer is the (DEA)
The Drug Enforcement Agency or (DEA)
Commonly referred to as "The DEA." It is an agency of the federal government dedicated to the enforcement of all laws dealing with drug policy.
cooperation, assistance, or respect of jurisdiction
The local law enforcement agency - Police.
Federal law enforcement agencies often assert jurisdiction in cases where state boundaries are crossed. However, very often the states themselves do as well.
It depends on the specific agency.
When assistance it is coordinated by a federal agency. This is with the primary jurisdiction.
In the United States, this is the DEA (Drug Enforcement Agency).