var data = {
  labels: ['W1', 'W2', 'W3', 'W4', 'W5', 'W6', 'W7', 'W8', 'W9', 'W10'],
  series: [
    [1, 2, 4, 8, 6, -2, -1, -4, -6, -2]
  ]
};

var options = {
  high: 10,
  low: -10,
  axisX: {
    labelInterpolationFnc: function(value, index) {
      return index % 2 === 0 ? value : null;
    }
  }
};

var chart = new Chartist.Bar('.ct-chart', data, options);

// Based on ty's comment
chart.on('created', function(bar) {
  $('.ct-bar').on('mouseover', function() {
    $('#tooltip').html('<b>Selected Value: </b>' + $(this).attr('ct:value'));
  });

  $('.ct-bar').on('mouseout', function() {
    $('#tooltip').html('<b>Selected Value:</b>');
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/chartist.js/0.9.5/chartist.min.js"></script>
<link href="https://cdn.jsdelivr.net/chartist.js/0.9.5/chartist.min.css" rel="stylesheet" />
<div id="tooltip"><b>Selected Value:</b>
</div>
<div class="ct-chart"></div>