a rap, a drum, a "dead horse"
things with beats, or things you can beat
dances
Athos, Porthos, Aramis
Musketeers
Alvin, Simon, Theodore
Chipmunks
Adam, Hoss, Little Joe
Sons on Bonanza
Umaga, Triple H, John Cena
Wrestlers
Hammurabi, Morse, Enigma Machine
codes
The butcher, the baker, the candlestick maker
Three men in a tub
Kentucky Derby, Preakness Stakes, Belmont Stakes
The Triple Crown (Horse Racing)
Larry, Mo, Curly
Three Stooges
Fort Sumter, Appomattox, Antietam
civil war battle sites
Tiger, mako, hammerhead
sharks
Dredd, Judy, Mike
Judges
Lombardi, Lord Stanley, Larry O'Brien
Trophies
bishop, knight, rook
chess pieces
Shitoism, Zoroastrianism, Jainism
religions
Matthew, Thomas, Kayla
Bright Side
Diana Ross, Florence Ballard, Mary Wilson
The Supremes
José, Luciano, and Plácido
Tenors (Carreras, Pavarotti, Domingo)
Jack, Janet, and Chrissy
Conrad "Nicky" Hilton, John Warner, Richard Burton
Liz Taylor's husbands
Bert, Grover, the Count
Sesame Street
Harry, Hermione, and Ron
Harry Potter
Proton, Electron, and Neutron
atoms
Amethyst, Topaz, Ruby
birthstones