If we’re planning to change the name of the thread from “Two-hit wonders” to “Two highly memorable role wonders” then I’d tend to agree.
To be fair, that’s kinda what the OP is suggesting.
Yeah. How big a “hit” does a movie have to be? 
Rocky Rambo
Back to music: Sugarloaf had two hits with “Green Eyed Lady” and “Don’t Call Us; We’ll Call You.”
Joe Walsh as a solo had two with “Rocky Mountain Way,” and “Life’s Been Good,” but had to ruin it all with “Ordinary Average Guy.”
Patrick Stewart = Star Trek/X-Men, and a dozen forgettable roles.
I was going to say Eagle Eye Cherry, but I checked and he really only had one song that was a hit “Save Tonight”. So I guess he’s more of a one hit wonder.
I can’t believe I forgot WW. Damn, Okay, not a two hit wonder for sure.
In the musical world, Murray Head had “Superstar” and “One Night in Bangkok.”
And absolutely, positively nothing else.
Most people remember him as “Han Solo” (which is one role, no matter how many movies he’s played it in) and “Indiana Jones” (same) and would be hard-pressed to name any of the other movies.
I thought this was going to be about music… in which case, I’ve got serious problems remembering more than two Bangles songs, but those two get tons of air time (Manic Monday and Walk Like an Egyptian).
Stallone was in “Lords of Flatbush” and some soft core porn flick.
Rowan Atkinson - Blackadder and Mr. Bean
Music - Men Without Hats: Safety Dance and Pop Goes the World. And I’m not ashamed to admit that I still a big fan of theirs.
Actors - Barry Bostwick: Rocky Horror Picture Show and Spin City (lots of stage work, but those are his two instantly recognizable roles)
“Shall we play a game?” WarGames
LadyHawke
And he might also be known for his role in the bomb Godzilla.
Yes, I clearly forgot those and he was one of the best things about LadyHawke – so, he’s off the list.
“Hazy Shade of Winter,” “Eternal Flame,” “In Your Room,” and “If She Knew What She Wants.”
In music: Corey Hart with Sunglasses at Night and Never Surrender
In movies: Michael Shoeffling In Sixteen Candles (Jake the heart throb) and Mermaids (the guy Winona Ryder falls for)
I can only think of two musical examples at the moment:
Procol Harem- “A Whiter Shade of Pale” and “Conquistador”
Golden Earring- “Twilight Zone” and “Radar Love”
re: Harrison Ford
add Working Girl
And for my own nomination… can anyone, off the top of their head, name a single song that The Association did aside from “Cherish” and “Windy”?