The issue-index currently lacks a "take" action for
unassigned issues. The idea is to simple put a "take"
into the column of 'Assinged To' if an issue is
unassigned. Clicking on this link is a very easy way
get this issue assign to the loged in user.

Simply place this into issue.index (patch included):

   <td tal:condition="request/show/assignedto">
     <span tal:condition="i/assignedto"
tal:replace="i/assignedto" />
     <a    tal:condition="not:i/assignedto/plain"
           tal:attributes="href
string:issue${i/id}?:action=edit&assignedto=${request/user/id}">--
take --
     </a>
   </td>