A Schwinn. Replaced my 10 year old GT. The tires weren't retaining air and the gears were clicky and sticky.
The Schwinn is awesome.

21 gear mountain bike, vertical grips, 18", I transferred my front light and back blinker and my horse shoe lock and four digit lock and now my Schwinn is as pimped out as my old GT (except it's an adult bike, my GT was for a 10 year old! Thus, the timely replacement...). Except my old GT had a water bottle holder, damn...
And it only cost $149.99! Got it at Meijer! I'm so high right now, srsly.
The kids at U of I will be like "Hey, who's that cool looking bike nerd?"
Yeah. They will be.