All have been worked pretty thoroughly, really.
Walker's campaign for student president did have an episode of stealing student newspapers that printed a negative story about him. What has come out of Marquette itself is something that sounds like Walker was a student in good standing when he dropped out.
What we know for sure about Walker's career at Marquette is that when it ended it wasn't just a few credits short of graduation. He was about a year's worth of credits away from graduation
I mention this observation in passing...the teajad exalts counter-narratives to causes and one of them is anti-intellectualism. Not having a university degree likely raises Walker in their eyes, in the same way the "Even a C student can become president" statement of W did.
Another allegation sure to re-emerge is that Walker fathered a child out of wedlock during his time at Marquette. That charge was made by a roommate of the alleged mother. The alleged mother herself has had nothing to say about it...which has led to rumors that she was paid hush money, which cannot be confirmed.