Simple Sale , 50 reviews
Works well, and it's reliable, but it's a bit TOO simple for the price. I'd love the ability to add more than one collection to be on sale at the same time (3-5 would be ideal). One is not ruseful if you have many different price tiers that you want to discount. The app is great if you do want to run a whole store discount or the same % off throughout.
The app worked fine when I ran the sale for Cyber Monday. I deleted it afterwards in hopes of the prices going back to normal but all the items were showing the SALE price. I didn't want to reinstall the app in case it ends up charging me. You have to manually change the price on each product individually.