Almost any champ can work if you play him/her enough to really know the ins and outs. That being said, out of your list here are some quick thoughts for ranked play. I'll asterisk the ones I think are worth your time.
LeBlanc: Very bursty champ. Not optimal for team fighting and little AOE.
*Lux: Great range and the shield offers at least a little support capability. Very squishy though
*Evelynn: Usually banned, awesome champ. Great for scouting and making the enemy team play defensively.
*Vladimir: Great champ, good aoe, good escape mechanisms, good damage. Popular choice but not usually banned.
Mordekaiser (NOT A TANK!): If you're not building tank, don't play Mord. The difference in damage between ap and tank builds is negligible and you'll get eaten for breakfast without tanking items.
Fiddlesticks (Jungle if possible): Squishy, damage is okay but not amazing. This guy is number one focus target because of his zero escape skills and low hp.
Cassiopeia: Been a bit more popular lately, but still rare in ranked games. Very squishy, Ult will screw you over half the time, decent damage and kiting.
*Malzahar: Popular champ. His ult is helpful for shutting down fed enemy champs in team fights. One of the best farmers, so you should always have high CS and be getting good items.
*Janna: Popular choice. Can be really annoying when played well, more often they're just a placeholder.
*Soraka: Another popular support. Can deliver enormous heals later on, Soraka can be a serious pain to lane against. The difference between a good Soraka and a bad Soraka is avoiding being focused in team fights while still being relevant.
Karma: Not enough damage, not enough heals, Karma is for people who want to be known for playing up champs well. Don't play this chick unless you've got something to prove.
*Nasus: Can be a great offtank; good players will go out of their way to deny him early on.
*Renekton: Solid champ, scales well into the end game. Build as offtank.
Gangplank: Another champ played by people with something to prove. So-so damage, good survivability because of built-in cleanse, nearly worthless ult.
Shaco: Can dominate early and mid game, but most players (including myself) cannot play him successfully if the game runs long. Must jungle.
Twitch: Worthless. Another champ for people with something to prove. **** damage, easily focused.
*Olaf: Great jungling offtank. The effectively zero cooldown on undertow rocks if you can hit a skillshot. This guy has a slight learning curve but becomes a rock star at end game, and is decent before that.
*Maokai: Pretty good tank, got some worthwhile damage and the snare is a decent initiator.
*Alistar: Still a game changer, despite umpteen changes.