There are several minor characters in the background of the story in Lost; known as 'Redshirts' (a term coined by Boone Carlyle for those who are expendible, as in the original series of StarTrek, security officers who make limited appearances are often endangered and/or killed).
The more prominent redshirts who play a central role in Lost are marked with this sign. "#"

List of Redshirts:

1. -Leslie Arzt # (Dead, Dynamite)
2. -Cindy Chandler. (From the tail section) #
3. -Edward Mars # (Dead, Injuries from plane crash)
   
4. -Steve Jenkins
5. -Scott Jackson (Dead, killed by Ethan Rom)
6. -Barbra Joanna Miller (Dead, Drowning)
7. -Richard
8. -Nathan, (From the tail section) #
9. -Zack. (From the tail section. Brother of Emma)
10. -Emma (From the tail section. Sister of Zack)
11. -Gary Troup (Also called the turbine man)
    
12. -Donald. (From the tail section)
13. -Nancy. (From the tail section)