## JavaScript: 4 tokens (** based on broad interpretation of "assignment"!)##

Obviously my score of 4 is extremely generous/lenient!

To arrive at that score I've assumed "assignment" (worth 0 tokens in the question) includes such things as additive assignment, subtractive assignment, multiplicative assignment, and XOR-ing (`^=`) assignment

<!-- language: lang-javascript -->

    function f(a, b, c) {
      d = a;
      d -= b;
      d = d >= 0;
 
      a *= d;  //a = a if (a>=b), else 0
      d ^= true; //invert d
      b *= d;  //b = b if (b<a), else 0

      a += b;  //a is now max(a,b)

      d = a;
      d -= c;
      d = d >= 0;
 
      a *= d;  //a = a if (a>=c), else 0
      d ^= true; //invert d
      c *= d;  //c = c if (c<a), else 0
      a += c;  //a is now max(max(a,b),c)

      return a;
    }

If those assignments actually count the score is 14 :)