Saw silverlight API at Dev conference, so this request for core (out-of-the-box) components is based on the templates previewed there, but can be applied generically across the API board:
(Not in any particular order):
1) Legend/TOC/LayerControl
2) Measure Tool
3) Scale and scalebar
4) Show coordinate(s)
5) Identify (default=generic, but customizable)
6) Query/Search (default=generic, but customizable)
7) Change Basemap (at runtime preferred), include Bing and Google Maps options.
😎 Markup
9) Ability to Mash-up (add layers - runtime preferred)
10) Include intuitive/robust default "Selection States" for API elements (hover and select)
11) Printing capability that inlcudes markups and dynamic layers
12) Run an asynchronous task (geocode should be default).