I never did this in undergrad, but grad lectures (especially for my thesis, which was basically how to cite APA style and use statistics - 2 things I already knew) were often completely worthless and it was really noticable if you weren't there (small classes), so I used to go and read digital comics. Easy to flip back and forth between that and jotting down lecture notes. I doubt I could've gotten away with games.
Ditto my old job. I had down time on Fridays (slow day) so I did the same thing. Wasn't exactly a secret though. My boss probably knew I did it. I usually had all my paperwork for the week done by thursday.
http://www.gitcorp.com/
They discontinued the Marvel ones though, which were the best. The Star Trek set is still really good though. The DC run of ST:TNG is surprisingly good.