1. At level 1 she has an AoE stun, if you took W first. This is useful for ganks and engages. Get your Pyromania passive ready, then tell your jungler to engage. Hopefully they have some form of CC also, and a double CC is very hard to escape.
2. Strong early and late game. She does not fall off later like some champs, and she is not weak early.
3. She has a great, safe farm ability with her Q. When you kill something with your Q, you recieve mana back, and the cooldown is reduced. It also helps stack up your passive stun
4. Quick damage burst.
5. Easy to play either offensively or defensively with equal success.
6. She's badass.

When you are trying to engage with intent of killing your opponent, make sure before you engage you have Pyromania ready. whith Pyromania up, use Deathfire Grasp , Summon: Tibbers, Disintegrate Incinerate, then if they are not dead by now (which they should be) make Tibbers chase them by holding down Alt and right clicking.

Annie's devil bear Tibbers has variety of uses, and is an extremely useful ulti. When Annie casts her ultimate ability, Summon: Tibbers it summons another allied unit called Tibbers. Tibbers can take damage, and be targeted by enemy spells and basic attacks. He can also basic attack, and has an AoE effect that does damage to everyone around him. Always try and summon him on a Pyromania stun spell. The size of the cast lets him stun the entire team, and then his fire burns them all while they are standing there. He can be used to tank tower, if you are trying to backdoor, help take dragon or baron nashor , and also be a huge benefit to teamfights. To control his movement, hold down the Alt key, and right click as if you were trying to move yourself, and he will move instead.

Annie is a very stong pick, in both Normals and Solo Queue. With practice, she is a beast to play. Just because she's a 450 champ, doesn't mean she is no good. Any champion, with practice and skill can do well. Except Zac. Zac sucks all the time. Good luck, and have fun burning things!