I was wondering if anyone knows the cut-off mark range for students that get accepted into one of the science co-op programs available starting 3rd year.

Most programs require you to have at least a 6.0 cgpa and completion of a set of courses.

6.0 for a limited enrollment program in high demand probably isn't going to cut it though and from anecdotal evidence I've been exposed to, you're generally looking to need an average of 9.5+.

Do co-op programs look at your work/volunteer experience, or do they work on the basis of GPA. If a person has a 9.5+ avg with very minimal work/volunteer experience, will he/she be accepted over a person with a lower average, but with more work/volunteer experience.

I'm really not sure.

I know a guy who lived on res with me first year who was basically a hermit and got into coop for chem, so I'm not sure if volunteer experience is a necessity.

I was accepted into the Biology & Pharmacology Science Co-op and I can say that marks are not everything. Most programs go through an interview process along with an application so that those in charge actually get to know you...so in that case, I would say experiences are beneficial because they shape who you are, but certain experiences (ie. lab work, or sciency jobs) aren't mandatory.