One of my latest favorites, is Crafty Carla's Amigurumi Pea-shooter from Plants Vs Zombies.
On Etsy you can find all kinds of Amigurumi patterns to make all sorts of stuff.
Chairy from Pee-Wee's Playhouse, a T.A.R.D.I.S from Dr Who, or even a Moogle!
With colorwork, knitting play along too. I think one of the best geeky knitted items ever is the Mario Scarf. I really hope Cass finishes it one day!
I've even gotten in on the action, with my Hermoine hat.
The pattern was written by a HUGE Harry Potter fan before the movie even came out. She did an awesome job for basing it off of just a publicity still!
What geeky craft have you made?