| 100% | AFRICA | 6 | The only continent in all four hemispheres |
| 69% | AFRICA | 6 | Only continent that lies in all four hemispheres |
| 69% | AFRICA | 6 | Only continent with land in all four hemispheres |
| 62% | AFRICA | 6 | Continent that's in all four hemispheres |
| 56% | PERU | 4 | Only four-letter country in the Western Hemisphere |
| 51% | EUROPE | 6 | Continent in the Northern and Eastern hemispheres |
| 50% | ASIA | 4 | The only continent where pandas live in the wild |
| 43% | ALOU | 4 | Surname of the only all-brother outfield in M.L.B. history |
| 43% | IOWA | 4 | Besides Ohio and Utah, the only state with four letters in its name |
| 42% | OMAR | 4 | Vizquel who's the only shortstop to play in four decades of MLB games |
| 41% | TSE | 3 | Only Asian security trading facility in the top four by market capitalization, for short |
| 41% | MOT | 3 | Monsieur Marceau spoke the only one in all of Mel Brooks's "Silent Movie" |
| 40% | GEORGIADOME | 11 | Only facility in the world to have hosted the Olympics, Super Bowl and Final Four |
| 40% | REDSOX | 6 | Only MLB team to win four World Series titles in the 21st century (2 wds.) |
| 40% | ASIA | 4 | Continent home to four of the five most populous countries in the world |
| 40% | JAMAL | 5 | ___ Crawford, the N.B.A.'s all-time leader in four-point plays |
| 40% | ICHIROSUZUKI | 12 | Outfielder who hit the only inside-the-park home run in an MLB All-Star Game (2 wds.) |
| 39% | ANAPEST | 7 | One of four in "'Twas the night before Christmas, when all through the house" |
| 39% | ASLAN | 5 | Only character to appear in all of the Narnia chronicles |
| 39% | THEATER | 7 | "The only institution in the world which has been dying for four thousand years," per John Steinbeck |
| 39% | ESME | 4 | Woman in all four "Twilight" novels |
| 39% | ANAPEST | 7 | It occurs four times in "'Twas the night before Christmas, when all through the house" |
| 39% | TOWN | 4 | The only game in ___ |
| 37% | KEANU | 5 | Reeves who starred in all four "Matrix" films |
| 37% | AUDRA | 5 | McDonald with Tonys in all four acting categories |
| 37% | ENS | 3 | The only consonants in "non-union" |
| 37% | PAULMILLSAP | 11 | NBA All-Star who signed with the Nuggets in 2017 after four years with the Hawks: 2 wds. |
| 37% | ASLAN | 5 | Only character in all seven Narnia books |
| 37% | ADDER | 5 | The only venomous snake in the UK |