CREATE TABLE table_203_60 (id DECIMAL, "outcome" TEXT, "no." DECIMAL, "date" TEXT, "championship" TEXT, "surface" TEXT, "opponent in the final" TEXT, "score in the final" TEXT)

which surface was used the least ?
SELECT "surface" FROM table_203_60 GROUP BY "surface" ORDER BY COUNT("surface") LIMIT 1
SELECT "surface" FROM "table_203_60" GROUP BY "surface" ORDER BY COUNT("surface") NULLS FIRST LIMIT 1