.icon-delete {
    background-image: url(../images/delete.png) !important;
}

columns : [{
    text : 'Name',
    dataIndex : 'name',
    width : '50%'
},
{
    xtype : 'actioncolumn',
    draggable : false,
    hideable : false,
    menuDisabled : true,
    width:'50%',
    items : [{
        iconCls: 'icon-delete',
        tooltip: 'Delete',
        scope: this,
    }]
}]

{
    xtype:'actioncolumn',
    width:20,
    items: [{
        iconCls: 'icon-delete',
        tooltip: 'Delete',
        handler: function(grid, rowIndex, colIndex) {
            grid.getStore().removeAt(rowIndex);
        },
        scope: this
    }]
}