What is the most ridiculous pessimization you've seen? [closed]

Answer 1

I once worked on an app that was full of code like this:

 1 tuple *FindTuple( DataSet *set, int target ) {
 2     tuple *found = null;
 3     tuple *curr = GetFirstTupleOfSet(set);
 4     while (curr) {
 5         if (curr->id == target)
 6             found = curr;
 7         curr = GetNextTuple(curr);
 8     }
 9     return found;
10 }

Simply removing found, returning null at the end, and changing the sixth line to:

            return curr;

Doubled the app performance.