Elise is a perfect one. She can switch to ranged and melee, so you can ease yourself in to learning ranged. Also, her assasin spider form focuses on getting up close and personal and autoattacking alot with you spidery buddies

volibear has built in attack speed, and his ult buffs each auto attack, and his w does tons of damage despite building tanky and does more damage the more hp they are missing. so it is a great executioner type of move, like cho's garen's darius's ultimates. except volibear's w is not nearly as powerful. but can be used from short skirmish to short skirmish, or near the end of the fight to really bring a hurtful move.

he is not that good though, most popular tops will beat a volibear. volibear can only reliably beat the less popular top choices like nasus, irelia, poppy, renekton. the only moderate top volibear can match up ok against is xin. but people like garen darius elise cho malphite panth olaf shen teemo. they all do well against a volibear. those executioner people just got stronger executes, due to it being on their ultimates. you can win against them, but it will be hard very hard. any one with a brain can totally out play volibear though. even at low elos they will counter your passive with ignite and you know just out play you, and they understand that you will try to execute them if they low, and that you are easy to kite.

If you want an easy to play AP assassin, go with Katarina. If you want a harder one, go with Akali or Kassadin.

Good AD assassins are Mantheon, Talon, and Kha'Zix.

All these champions blow up enemy carries, but they all start to fall off late game if they aren't fed enough.

Serious question: What weaknesses are you interested in?

Every character has tradeoffs. If you play as an assassin with high burst damage, the tradeoff is typically low sustained damage. High attack speed makes no sense for an assassin unless they're the "sticky" kind of assassin. Not with high burst damage, but the ability to get to and stick to a back row target as they try to get away and/or their team tries to peel them off of you. Nocturne and Olaf come to mind.

All of the previously mentioned suggestions are great, but I still have to recommend my personal favorite: Lee Sin. He doesn't really utilize attack speed, but he does have a 40% AS boost permanently as long as you spread out your spell casts. He is a crossover between assassins and bruisers, and as such is an excellent duelist. He does drop off late game, but until then he can fight anyone to the death. His strongest point is his early game. His burst damage is godlike until the enemy buys heavy armor.

He is much more difficult than most champions, so try him out on a free week before buying him so you know what you're getting yourself into.

This free week has a few melee bruiser choices. None of them are my primary choices, but I prefer more spell-focused champions. Your mileage may vary.

Sion - He's got impressive DPS with his toggled AD boost and ult that gives AS/Lifesteal. If you go AD Sion, you're a glass cannon. Kinda tricky to figure out, but pretty darn scary in the right hands.

Wukong - Friggin jukemaster. You've got a decoy to trick the enemy laner, a dash that gives you attack speed, armor shred, and a pretty strong ult.

Shyvana - Manaless speed demon. She sticks to targets and has pretty good sustained damage. Heavily autoattack-based though.

If you're looking for an AP assassin... as Megaman said, what are you willing to trade off? Most AP assassins contribute to a teamfight by taking out one target very quickly. You're pretty much dead after that, unless you can escape. You'll have to trust that your teammates can initiate teamfights, and keep attention away from you until you've gotten the kill.

Xin is the clear choice

This will probably get devoted, but for a ranged assassin type Teemo is just pure fun. He counters melee camps hard with his blinding dart that makes them miss attacks for up to 2.5 seconds. He has a built in speed boost that lets him chase down runners and get away from other assassins. His damage mostly comes from his poison dart and shrooms that just get nastier as you build ap. He is cheap to get too. Look for the AP Teemo build on mobafire.com. He can be addictive if you really like tolling the enemy team. He is squishy and there is a lot of hate for him out there so be prepared to get focused when you start to snowball.

I really appreciate all the help guys! I just don't want to play a character who is banned a lot in ranked games. I usually do not play ranged characters because I still haven't figured out how to maximize their damage efficiently but I am willing to look at a few. Ahri and Twitch look pretty cool.