Keyed collections are general purpose and will solve most commercial problems. However, there are other more specialized types of collections that offer more tuned performance and different functionality:

• Array collections are used where information is stored in a contiguous sequential order and only ever accessed by an index.  In such situations they are substantially faster then keyed collections. Array collections are suitable for, for instance, fast look-ups. 
• List collections are used to pass around large lists and in drag and drop operations. List collections can be merged together. List collections are unordered and therefore inserts to them are fast.
• Sorted array collections constantly maintain sort order, also after inserts.

Array Collection Example
List Collection Example 1
List Collection Example 2
Sorted Array Collection Example