After using the mega items option, I can't upgrade any weapons with mods or the game will crash. Also the unlimited sprint option doesn't seem to work for me. Not complaining, just trying to help! You guys are the Best!
Seconded for the unlimited run- it doesn't seem to work after the first level. I haven't tried any weapons upgrades, so can't weigh in there; though.
@Harshmage: Really, you don't need more than 1 energy bar if you're using unlimited energy, it's only a visual at that point.