Two more actions for Magento's own cart price rules, with everything a rule already has: conditions, coupons, dates, customer groups, priorities. 3 for 2, second item at half price, a free gift added to the cart when the rule applies and removed when it stops applying.
The two extra actions in a cart price rule.
What it does
Every Nth item, the cheapest, X% off
Free gift: a product added and removed by the rule
