if you want real advice, go to the training and/or cardio boards, genius.
do a search for HIIT and you will find endless threads arguing whether HIIT or moderate cardio is better for not losing too much muscle mass.
personally, I hate running. I like HIIT and I also do some other things like biking and plyometrics.
if you want to have some real fun, try some strongman type training (farmers walks and sled dragging are what life is about)