Add event in RadHyperlinkButton, that allows you to cancel the click action and replace it with custom one. The event can be executed only if the url is invalid, so you can decide if you should leave the default exception that is thrown in this case or if you want to cancel the opening action and implement custom action. 

The RadSplitButton implements the IDisposable interface, but its Dispose method cannot be overridden. Make it protected virtual so its default logic can be extended or replaced when creating a custom button class.

Enable controlling the alignment of the control's content through the HorizontalContentAlignment and VerticalContentAlignment properties.

The native radio button supports validation. Implement validation for the RadRadioButton

When IsThreeState property is true, after each click values of IsChecked property cycle like this: null -> false -> true. I would like to reverse this order to null -> true -> false in some cases and a property controlling that order would be a great help.

Implement mechanism that allows positioning the drop down content of RadDropDownButton when the DropDownPlacement property is set to Absolute or Relative. Something like DropDownHorizontalOffset and DropDownVerticalOffset.

*  3 Image properties (normal, hover, disabled)
 *  showBorder/flat true/false (Essentially making only the image appear as a button)
 *  if the 3 images are not set then the visual state manager should modify the image to appear disabled or hover with a highlight / mask overlay (or whatever the proper term is).

Should work the same as the RadContextMenu. 
Also add support for setting effect (DropShadow... ) to the Dropdown itself.

Make the image inside the buttons to be aware of the FlowDirection.

Add Closing event.

Implement functionality similar to http://demos.telerik.com/aspnet-ajax/button/examples/togglebutton/defaultcs.aspx

Add a visual representation for the IsDefault property like in Microsoft's button.

It should be possible to specify whether the drop down should stretch to the width of the button or whether it should be left - right aligned. The same should apply for the vertical positioning when the popup appears left or right of the button.

In that way it will be easy to set the popup animation to be slide, fade or scroll without setting a custom template. 

Available in R1 2017 Release

Close the DropDown popup when clicking on the DropDownContent in DropDownButton.

Available in R3 2016 Official Release.

An updated button that appears and acts like a hyperlink but is really a button with no borders but respects the enabled / disabled and all the visual states. 

 *  link should be disabled / grayed out if not enabled or if command guard is not enabled 
 *  could manage the 'visited' as a pressed (not interested in that for me, I just like the simple visual).
 *  the samples/demos homeview provides a nice example where the long text is highlighted and presents the hand icon. The re-styling is however 6 pages long and cumbersome to copy as it references other parts of the sample project (I tried)

A button with state that looks like a switch.

We have created a SDK sample demonstrates how to style a RadToggleButton to look like a Toggle-Switch button. 
You can find the example in out SDK repository(https://github.com/telerik/xaml-sdk/tree/master/Buttons/ToggleSwitchButton)

Clicking on the RadSplitButton in XAML opens the designer unexpectedly

Available in LIB version: 2015.1.0309