Speaking of Diet Coke... you can put a can of it into a regular chocolate cake mix in place of the butter/oil/eggs, mix it just to get it blended and bake it and you'll have a really good chocolate cake,
Apparently with this cheesecake recipe, you can substitute lo-fat rolls and cheese, use that artificial spread in place of butter and substitute Splenda for half or more of the sugar and it's still delicious. I'm going to try that next time.
I'm also going to sneak a can of cherry or lemon pie filling in between the cheese layer and the top crust and not put any cinnamon in the butter.