1. Radio-buttion with Checkbox Behavior:
This plug-in will modify radio-buttons usual behavior that once selected there will always be one radio-button which will stay selected from the group instead you can select and by clicking on same selected radio-button you can deselect it.
2. Fancy Radio-button/Checkbox (Custom Control) Plugin:
jQuery Plugin for Fancy Custom Checkbox and Radio-buttons makes form elements visually more expressive.
3. DG Magnet Combo (Multi-select with no CTRL Click):
This is jQuery plugin which eliminates requirement to keep CTRL (Control) key pressed while using html-select control (combo/listbox) and user can select multiple options without hassles of keeping CTRL-key pressed. (Many times for longer lists it's headache.) Along with that it promises natural functionality even if used with CTRL-key pressed.