So, I may have taken this challenge and way over-researched it, trying to come up with suitable houses for the Lost characters. (Even doing hybrid houses for a few.) And that was after sorting all the Lost characters into the "This Is War" lyrics before realizing someone had already done that. Then I decided I was going overboard. So, instead I picked a character for each house from La Femme Nikita, Legend of the Seeker, and Lost. Much easier. :)
Gryffindor
Jurgen, La Femme Nikita
James "Sawyer" Ford, Lost
Zeddicus Zu'ul Zorrander, Legend of the Seeker
Hufflepuff
Nikita, La Femme Nikita
Hugo "Hurley" Reyes, Lost
Richard Cypher, Legend of the Seeker
Ravenclaw
Kahlan Amnell, Legend of the Seeker
Daniel Faraday, Lost
Birkoff, La Femme Nikita
Slytherin
Michael, La Femme Nikita (although like 90% of the primary characters would go here!)
Cara, Legend of the Seeker
Ben Linus, Lost
This was fun!