EG Auto Add to Cart Free Gift

Easy to set up, great variety of rules, works like a charm. Shopify spoils it a bit though by making it impossible to combine some types of discounts, so if you're using BOTH coupons or affiliated discounts and free gifts with order promotions, you may have to create 0-priced products for this purpose. (Yes I made my discounts compatible with other discounts, no it didn't work). Very happy with the app, rather annoyed with Shopify.