(This a huge favorite because basically everyone loves cucumbers and because it's very easy to make.)
3 tablespoons mayonnaise
Add enough milk to make the dressing smooth*
1 tablespoon vinegar
1/2 small onion sliced into very thin 1 inch strips.
1/2 teaspoon sugar or Splenda
1/4 teaspoon salt (optional)
Mix the mayonnaise, milk, vinegar, sugar and salt together in a small bowl. Mix until smooth.
Peel and slice the cucumber very thin. Pour the sauce over the cucumber and onions; serve. *If you add too much milk, just add more mayo.