Maybe you've heard of Jeffrey Combs. He has done movies like Re-Animator, The Frighteners and I Still Know What You Did Last Summer but is known (in my circles) as the best Star Trek guest actor EVER! He has played at least 7 different parts on Star Trek DS9, Voyager and Enterprise.
Weyoun is the most popular of these characters. He was a Vorta and served as a second in command of the Dominion. There were actually 8 Weyoun clones and he played all of them. He had an eerie charisma and always had the best lines. If you ever hear Walls and I say "Time to pack!" it's in reference to Weyoun.
Brunt was the Ferengi that even other Ferengi hated. Always one-upping Quark and trying to lead the Ferengi he was another great character.
Shran is an Andorian Commander and sometime helper on Enterprise. I'm only 14 episodes into the first season of Enterprise but he's already been on the show twice. And Combs is brilliant as always.
Combs stars in all kinds of B-Movies and guest spots on television. Even playing Captain Cold on THE FLASH television show. He is such an under rated actor. I recommend watching Star Trek...period, but watching the episodes with Combs makes it that much more pleasurable.