Please consider adding animation to the slider control in a similar way to the linear gauge or the ajax slider control.  this would add an extra dimension to the controls capability

Build a Kendo Pie chart with long label names in the legend.
Hover the chart close to the legend - if the area around the chart is too crowded with legend labels the tooltips (supposed to be displayed in that area) are actually placed very far from the chart, leaving the chart container.
Maybe it would be beneficial to replace the absolutely positioned tooltip <div> with an svg representation.

Hi,

some of date and time patterns defined for cs and cs-CZ cultures are wrong. The correct patterns are:

d: "d. M. yyyy",
g: "d. M. yyyy H:mm",
G: "d. M. yyyy H:mm:ss"

(dots are followed by spaces)

Have the opportunity during the reporting grid columns to add or hide visible property. This then avoids calling the function hideColumn.

By default the column is visible.

HTML input of type file has a "false" default value for multiple whereas KendoUI has it set to true. In addition, KendoUI ignores multiple attribute in input definition while it uses it for the emitted HTML.

Hi,  It would be better to change grid slightly to accept dynamically changing automatically 

the baseUnit option is great; it offers us minutes, hours, days, months, years.. but not weeks. I would like to see an option to break down the granularity in weekly format.

...similar to a detail template, I'd like to be able to nest a Kendo grid of child records in single cell of a parent row.

Multi-column Headers like the asp.net ajax grid 

http://www.telerik.com/products/aspnet-ajax/grid.aspx

I want to have more options for tooltips that work like facebook's tooltips - you get a box, a strip at the bottom w/ buttons. I would like this for the modal windows as well as any tooltip/menu item. 

Some sort of scaffolding for adding buttons to a flyout window component.

Sometimes need to disable column selectable option. For example, when column consists checkboxes or action buttons.

$("#users-grid").kendoGrid({
  dataSource: {
    data: createRandomData(20),
    pageSize: 5
  }
  selectable: 'row',
  columns: [
    {
      field: 'UserId',
      title: 'ID',
      template: '<input type="checkbox">',
      selectable: false
    }
    {
        field: "FirstName",
        title: "First Name"
    },
    {
        field: "LastName",
        title: "Last Name"
    },
    {
        field: "Actions",
        title: "Actions",
        template: '<a href="">Delete</a>',
        selectable: false
    }
  ]
});

and a grids toolbar with the commands and template at the same time throw a search input text that filters the grid. 

In a kendoTreeView if I define the dataSource as an observableHierarchy, then expand(".k-item") expands only the first level but if I execute it twice!!! it works correctly

add the ability to choose the weekly in datepicker

There is a bug when cancelling the edit of a row that was loaded through virtual scrolling from a remote datasource, the row disappears from the grid/datasource. Telerik confirmed they can reproduce the bug but due to the specificity of the virtualization process currently do not plan to provide a solution for this. Their recommendation is that if you need editing with a remote datasource to disable virtual scrolling and enable paging instead. Vote for this to have the bug fixed.

I have a master detail grid and simply would like to place captions on them.

The js executes successfully, but the captions don't appear when the View is fully rendered.

Grid._toolbar function:
toolbar = isFunction(toolbar) ? toolbar({}) : (typeof toolbar === STRING ? toolbar : that._toolbarTmpl(toolbar).replace(templateHashRegExp, "\\#"));
if toolbar a function, you don't escape # characters, which results in invalid template function generation

Input Mask is very  basic requirment but Kendo UI dont have such Mask Controls.