There are quite a few catalog/deals/specials applications, but mCatalog - Catalog of Deals is my favorite. I like the deals they have
(discounts are often 40% - 50% or more on relatively big ticket items - outdoor and sports gear), and also their inteface and design.
It is so easy to browse and search the deals, view all details in one place (no need to click multiple times to see more and more details), and I like the way you can play with images - you can move them around, zoom in and see all parts of an item in details.

Also, new deals are automatically downloaded to your catalog - so you can look through new deals once in a while without waiting for them to download, and you can do it even when there is no connection - you just need connection when you actually placing an order. You can always add item to favorites and order later if no connection is available now.

All in all - good application, nice to have it on your phone.