An interesting genre you may want to try is the Typing Game. My first experience of this was The Typing Of The Dead (a tacky sequel to House Of The Dead). It looked rubbish, but after about 10 mins you found yourself screaming "such a bad game! So... why... can't.... I ... stop... playing!?"
You could do a form of sidescroller along that same basic vein. Enemies appear with text over their head. You have to type the text in order to damage them. Each letter you press correctly does more damage. Get a letter wrong, and it does nothing.
In your game, you could have a basic line-of-sight system where the player is always firing objects in the direction of every on-screen enemy. If the object hits the enemey without being blocked by obstacles, then the enemy is in sight. If this is the case, it displays the text above the bad guy's head, and he gets added to the list of enemies you can 'tab' through. Each time you press 'tab', it cycles your focus to the next visible enemy (shift+tab cycles the opposite way). If an enemy walks out of your line-of-sight (eg: under a platform, or behind an obstacle), then you lose focus and you can no longer target them.
They start with easy text, like "Fred", "Bob", "Jack", "Claire", but gradually get longer - "Jefferson", "Gillian", "Michael", "Anderson", "Jackson", "Jonathon", "Phillip", and so on. As the game gets worse, you get two names, "Martin Muggwotch", "Bob Dylan", "We Couldn't Be Bothered", "Need 4 Deoderant", etc. You may be able to throw in extra special bad guys who have special characters like "¶" (ALT+0182).
Anyway, story. Little Bob was a disturbed child who used to go to sleep when he was 5, and dream of a world filled with weird fluffy animals and trees made of pillows, etc, etc.
Now he's 10, he suddenly dreams of the same world once again - this time it's filled with puffins trying to take over. To get rid of them he must use his power of geekage to type their 'name'.
I was thinking of some futuristic fantasy game, i.e. dragons in concrete lairs, with the main character being some chick with special magical powers, being hunted down by the government's anti-magic squads, and her assistant being and old elven sheriff (rather than the usual annoyingly cute sarcastic creature).
But then... I just don't know how to continue the story. There's so damn many ways to go that I end up spinning in circles with a really crappy storyline that seems similar to those cyberpunk vampire games. Main character's under 18, so no bars or nightclubs .
Disclaimer: Any sarcasm in my posts will not be mentioned as that would ruin the purpose. It is assumed that the reader is intelligent enough to tell the difference between what is sarcasm and what is not.