columnDefs
now accepts a class. I'd say this is the preferred method if you'd like to specify columns to disable in your markup:
<table>
<thead>
<tr>
<th>ID</th>
<th>Name</th>
<th class="datatable-nosort">Actions</th>
</tr>
</thead>
...
</table>
Then, in your JS:
$("table").DataTable({
columnDefs: [{
targets: "datatable-nosort",
orderable: false
}]
});