[Rasy]

Sinevik,
или замени e на event.

function ShowMe() {
       *!*
        var c = e.target;
        */!*
        var f = c.textContent;
        console.log(f);
      }
      
      var a = [1, 2, 3, 4, 5, 6 ,7, 8];
      for(var i = 0; i <= a.length; i++){
        var b = document.createElement('p');
        b.textContent = a[i];
        b.onclick = ShowMe;
        window.document.body.appendChild(b);

      }