One of the things that I gave up for lent was eating school lunch (I was working in a school at the time) and by doing this I lost 5 pounds in one week!! This ended up being a tradition I stuck with and have not eaten a school lunch since. I think that one of the big wins on that was bringing lunch from home was better for me because there was less processed foods and I controlled the portion size.
Something that I found I liked to do during this 40 days, was add something to my life that was positive. One year I took a photo with a camera everyday for the 40 days. Another was stop using plastic one time use water bottles, I haven't used one since, just reusable ones. The Lent promise that stuck out the most was running everyday of Lent.
It was a great experience and I ran in some pretty crazy places and situations. After I ran for the whole year I wrote a book about the experience named Running 365.