A frequent question relates to using a Data Validation drop down box with a LARGE set of options. If there are 100 names or choices to choose from, the user is looking for a way to not have to scroll down through 80 names to get to Wilford. The AutoComplete feature available in the Control Toolbox drop down boxes isn't available for the simpler in-cell Data Validation drop down.
So, here's a semi-workaround. This technique won't autocomplete as you type, but it will help you navigate a lot of options quickly in a single cell.
It's also great for creating in-cell drop down dependency, cascading from one set of options to another in the same cell rather then using several cells, as is more common.