Answer: GMEN
GMEN is a crossword puzzle answer that we have spotted 65 times.
    - F.B.I. figures
 
    - "The X-Files" extras
 
    - X-file examiners
 
    - Feds
 
    - They're on big cases
 
    - Some gangbusters
 
    - 1935 James Cagney crime film
 
    - ___ Detective (1930's-50's crime fiction magazine)
 
    - *Backup for Dick Tracy
 
    - Hood fighters
 
    - Agents under J. Edgar Hoover, informally
 
    - Some raiders, informally
 
    - FBI workers, slangily
 
    - FBI figures
 
    - Some FBI employees
 
    - FBI guys
 
    - Fed. agents
 
    - Some Feds
 
    - Some agts.
 
    - The Bureau's agents
 
    - FBI agents
 
    - New York footballers, to fans
 
    - F.B.I. operatives
 
    - 1935 James Cagney movie
 
    - FBI's guys
 
    - Cagney film of '35
 
    - FBI operatives
 
    - FBI guys, e.g.
 
    - Ness' co-workers
 
    - Hoover's staff
 
    - Dillinger's chasers
 
    - Hoover's force, briefly
 
    - "The Untouchables" heroes
 
    - Hoover underlings
 
    - F.B.I. guys
 
    - Fed. investigators
 
    - Racketeer busters
 
    - Gangster film extras
 
    - Fed personnel
 
    - Original name of the radio show "Gang Busters"
 
    - Pursuers of the Sopranos, for short
 
    - Dillinger's foes
 
    - Federal agts.
 
    - New York NFL team, familiarly
 
    - FBI agent
 
    - 1935 Cagney crime film
 
    - Agts. who might use the starts of 20-, 34-, 42- and 56-Across
 
    - See 36-Across [get weekly puzzles @avxwords.com for just $15/year]
 
    - Cagney classic of 1935
 
    - Fibbies
 
    - Mafioso foes
 
    - Mafia menacers
 
    - Govt. agents
 
    - Some raiders
 
    - Figures in 2011's "J. Edgar"
 
    - Guys in "J. Edgar"
 
    - FBI agents, slangily
 
    - FBI personnel
 
    - Investigators
 
    - 1935 Cagney and Dvorak movie
 
    - Guys working in the Hoover Building
 
    - 4-Down personnel, informally
 
    - New York football team, to fans
 
    - New York football team, informally
 
    - N.Y. footballers, to fans