Suggestions by @darke

Chace Crawford

as Sam Scudder in The Flash 2

Edgar Wright

as Director in The Flash 2

Rahul Kohli

as Dr. Ray Palmer in The Flash 2

Josh Lawson

as George Harkness in The Flash 2

Alfre Woodard

as "The Wall" in The Flash 2

Amanda Waller

as "The Wall" in The Flash 2

Spoiler

as "The Wall" in The Flash 2

Antony Starr

as "The Haunting" in The Flash 2

Eobard Thawne

as "The Haunting" in The Flash 2

Spoiler

as "The Haunting" in The Flash 2

Forest Whitaker

as Dr. Silas Stone in The Flash 2

Michelle Monaghan

as Nora Allen in The Flash 2

Edward Norton

as Henry Allen in The Flash 2

Teyonah Parris

as Lisa Snart in The Flash 2

Michael Mando

as Mick Rory in The Flash 2

Donald Glover

as Leonard Snart in The Flash 2

Daisy Ridley

as Iris West in The Flash 2

Ben Hardy

as Barry Allen in The Flash 2

Giancarlo Esposito

as Dr. Hugo Strange in Batman: Book of Fear

Giancarlo Esposito

as The Doctor in Arkham Asylum: Silence of the Sick