Forest's movie appearances over the years have spanned from war films to horror to comedy; among the highlights:
GHOST DOG: THE WAY OF THE SAMURAI (1999)
THE CRYING GAME (1992)
BIRD (1988)
GOOD MORNING, VIETNAM (1987)
PLATOON (1986)
FAST TIMES AT RIDGEMONT HIGH (1982)
And much, much more -- this is just a snapshot of his career, which also includes a slew of additional acting credits (and appearances in well-known TV shows) and a history in both producing and directing.
Check out his full bio and resume on the Internet Movie Database (imdb) here.

His acting in "The Shield" is on par with anything he has done on film.