I do not mean to say what actor should have gotten the role, or should have tried for a role, but in general if you think an actor could have portrayed a character in Star Trek. So I guess only as a Guest Appearance...
Perhaps it would be best if we keep it in terms of actual possibilities, so only those who could have gotten a role when any Star Trek was produced - which would probably exclude most non-US actors.
Just today have been thinking about these:
Martin Landau as a Vulcan/TOS
Hugo Weaving as a Vulcan/ENT
Tim Curry as a Q/TNG

Perhaps it would be best if we keep it in terms of actual possibilities, so only those who could have gotten a role when any Star Trek was produced - which would probably exclude most non-US actors.
Just today have been thinking about these:
Martin Landau as a Vulcan/TOS
Hugo Weaving as a Vulcan/ENT
Tim Curry as a Q/TNG
