Marinades damage the structure of the meat, making it more tender–but also mushy. They penetrate less than 1⁄4 inch and can leave residues on the meat surface that burn during cooking. They are, in my opinion, useless.
If you need to tenderize your venison, brine instead. A brine penetrates deep into meat–and carries flavor with it. The salt solution also prevents the meat fibers from toughening up as much and helps the meat retain moisture.
Start with a brine of 2 tablespoons of salt per quart of water and add flavorings from there. Suggestions? Bay leaves, juniper berries, cracked black pepper, chile pepper, thyme, celery seed. Last tip: Don’t brine for more than a day, or you risk having very salty meat.