In any comicbook, especially one written by Mark Waid, the characters that inhabit the make believe world of The Flash are the most important element of the series that make readers return to the book, issue after issue.
Jay Garrick (Flash I)
Barry Allen (Flash II)
Wally West (Flash III)
The Dark Flash
Bart Allen (Impulse)
Max Mercury
Jesse Chambers (Jesse Quick)
Johnny Chambers (Johnny Quick)
Dick Grayson (Nightwing)
Donna Troy (Troia)
Alternate Reality / Future heroes
Cobalt Blue
The Black Flash
Neron
The Rogues Gallery
Professor Zoom
Abra Kadabra
Kilg%re
Linda Park
Angela Margolin
Iris West
Hartley Rathaway (Pied Piper)
Chester Runk (Chunk)