The Prompt With List action (v8+) lets you select from a list of values. The values should be placed on separate lines, and can come from a clipboard, variable, file or text within the action.
You can include a title (which is only displayed when the search field is empty), as well as a default search string (v8.1+). You can also configure the width of the window (narrow, normal, wide, automatic) and whether to allow multiple selections (v8.1+).
If a single entry is returned, it is returned by itself (no newline character). If multiple entries are returned, they will be returned as multiple lines, each followed by a newline character (8.1+).
If there is no title and no search string and less than 100 items, then all the items will be shown. Otherwise only matching items will be shown until you search for something.
The values are displayed in a Spotlight-like window, similar to the Trigger Macro by Name action.
The selected item will be saved back to the source of the list, or to a specified clipboard, variable or file.