- Only state with a two-vowel postal code
- Only state with homonyms
- Only state with two Ivy League schools
- Only Stratego piece that can take a marshal
- Only Stratego piece with a letter on it
- Only Super Bowl the Eagles won
- Only Super Bowl won by the Jets
- Only Super Bowl won by the New York Jets
- only surviving representative of the order Apterygiformes
- Only team besides the Yankees to win three consecutive World Series
- Only tennis player to have won each Grand Slam event at least four times
- Only tennis player who has won all four Grand Slam titles at least four times each
- Only the credits held my attention et al.
- Only the Good ___ Young
- Only the Good Die Young performer
- Only the hand that ___ can write the true thing: Meister Eckhart
- Only the Lonely actress Maureen
- Only the Lonely crooner
- Only the Lonely singer
- Only the Paranoid Survive author ___ Grove
- Only the Young band
- Only theoretical
- Only thing between you and an open window?
- Only thing I have for you?
- Only this, and nothing else
- Only three-letter astrological sign
- Only three-letter constellation other than Leo
- Only three-letter scale note
- Only three-letter sign of the zodiac
- Only three-letter word in Scrabble that requires both blank tiles
- Only three-letter zodiac sign
- Only three-VP CIC
- Only Time New Age singer
- Only Time New Ager
- Only Time singer
- Only Time singer, 2001
- Only Time songwriter
- Only Time Will Tell rock band
- Only Time Will Tell singers
- only to a choosen few
- only to a chosen
- only to a chosen few
- only to choosen few
- Only Triple Crown winner who wasn't Horse of the Year
- Only two alphabet letters have them
- Only two U.S. states, Wash. and Cal., are entirely within this zone
- Only U.N. member whose flag is not rectangular
- Only U.N. member whose name comes alphabetically between P and R
- Only U.S capital sharing no letters with its state.
- Only U.S. marsupial
- Only U.S. pres. to resign
- Only U.S. president also to serve as chief justice
- Only U.S. president born in Hawaii
- Only U.S. president to have three veeps
- Only U.S. president whose surname is more than 50% vowels
- Only U.S. senator with a unit of measure named after him
- Only U.S. state in which the name of the state and its capital share no letters: Abbr.
- Only U.S. state whose flag isn't rectangular
- Only U.S. state with a non-rectangular flag
- Only U.S. state with a pennant-shaped flag
- Only U.S. state with a Spanish motto
- Only U.S. state without a rectangular flag
- Only U.S. vice president born in Maryland
- Only unanimous Baseball Hall of Fame electee
- Only unanimous Cy Young Award winner between Dwight and Randy
- Only United Nations member whose name starts with "O"
- Only US president to receive both a Purple Heart and a Pulitzer Prize
- Only US state that can be typed on one row of the QWERTY keyboard
- Only US state with two official languages
- Only veep born in DC
- Only veep from Maryland
- Only vegetable never sold frozen, canned, processed, or cooked
- Only vice president born in D.C.
- Only wants for sex, say
- Only Welsh-born Batman
- Only what a person can take?
- Only When I Laugh actor James
- Only winner of People's Sexiest Man Alive who's no longer alive
- Only winner of six straight European Figure Skating titles besides Sonja
- only winners need apply
- Only with for the money, say
- Only woman aboard the Argo, it's said
- Only woman to sing lead vocals on a Beatles song
- Only woman to win the top prize on "The $64,000 Question"
- Only woman with two Nobel prizes, formally
- Only word containing three consecutive pairs of double letters
- Only word heard in a 1958 song of the same name
- Only word spoken in Mel Brooks's "Silent Movie"
- Only word that's a two-digit number backward
- Only World Series perfect game pitcher
- Only You band
- Only you can prevent __ fires!
- Only you can prevent forest fires spot
- Only You new wave duo, as known in the U.K.
- Only's partner
- Ono from Tokyo
- Ono who co-founded Artists Against Fracking
- Ono's love
- Onomastician's study
- onomasticon
- onomatopoeia
- onomatopoeia as a source of word formation
- onomatopoeic
- Onomatopoeic bird
- Onomatopoeic Black Eyed Peas hit of 2009
- Onomatopoeic cry
- Onomatopoeic dance
- Onomatopoeic mint name
- Onomatopoeic musical effect
- Onomatopoeic sound
- onomatopoeic words are imitative of noises
- Onomatopoeically named legume
- onomatopoetic
- Onomatopoetic derision
- Onomatopoetic sound in KRS-One's "Sound of da Police"
- Onomatopoetic water sound
- Onrush
- Onscreen pointers
- Onsen soaks
- Onset
- Onset of a plot
- Onset of boredom?
- Onset of evening
- Onset of melting
- Onset of phobia?
- Onset of wakefulness
- Onsets
- onshore
- Onslaught
- Onslaught of cold weather
- Onslaughts
- Onstage blunder
- Onstage digression
- Onstage ham
- Onstage host
- Onstage hosts
- Onstage strutters
- Onstage surprise
- Onstage thought balloon
- Onstage thought bubble
- Onstage, say
- OnStar provider
- Onstar suggestions (abbr.)
- Ont. adjoiner
- Ont. appliance maker
- Ont. constabulary
- Ont. neighbor
- Ont. or Que.
- Ont. or Sask.
- Ont. police service
- Ont. summer time
- Ont. time zone
- Ont. time.
- Ont. town with Neil Young museum
- Ont., for one
- Ont.'s Capital
- Ontarian's interjections
- Ontario community or Polish namesake
- Ontario address
- ONTARIO agricultural provincial winter fair site (Can.)
- Ontario anagram
- Ontario and Michigan
- Ontario athlete, or 45-Across
- ONTARIO automobile industrial site
- Ontario border lake
- Ontario capital
- Ontario city
- Ontario city just west of Buffalo
- Ontario clock setting (abbr.)
- Ontario community
- Ontario community or English namesake
- ONTARIO county
- Ontario folk festival
- Ontario Fort
- ONTARIO government seat
- Ontario heritage river
- Ontario Hockey League team from Erie
- Ontario Indian
- Ontario Indians
- ONTARIO iron and steel industrial area
- Ontario is on it
- Ontario lake
- Ontario locale
- Ontario metropolis
- Ontario MLB city: Abbr.
- Ontario native
- Ontario natives
- Ontario NBA city: Abbr.
- Ontario neighbor
- Ontario neighbour
- ONTARIO oil-field site
- Ontario or Michigan
- Ontario or Supérieur
- Ontario politician Bob ___
- Ontario Port
- Ontario port opposite Port Huron, Mich.
- Ontario Premier 1971 to 1985
- Ontario Premier, formerly
- Ontario Premier, once
- Ontario raceway
- ONTARIO river
- Ontario river to James Bay
- ONTARIO Shakespeare Festival Theatre, site of the
- Ontario town
- Ontario town across from Buffalo
- Ontario town and French namesake
- Ontario town and British namesake
- Ontario town or actress Hilton
- Ontario town whose sign boasts a giant elephant
- Ontario tribe
- Ontario valley
- Ontario village
- Ontario-based music gp.
- Ontario-born hockey legend
- Ontario-born hockey legend Bobby
- Ontario-Huron link
- Ontario, e.g.
- Ontario, for example
- Ontario, for one
- Ontario, par exemple
- Ontario's ___ Canal
- Ontario's ___ Canals
- Ontario's ___ Locks
- Ontario's ___ Tower
- Ontario's ______ Dick
- Ontario's ______ Hill
- Ontario's ______ Lake
- Ontario's ______Bernardo
- Ontario's ______Demeter
- Ontario's 21st premier
- Ontario's 23rd Premier
- Ontario's bird
- Ontario's capital
- Ontario's capital on a sports ticker,
- Ontario's capital, on a scoreboard
- Ontario's capital, on scoreboards
- Ontario's capital, on sports tickers
- Ontario's Fort ___
- Ontario's Fort ______
- Ontario's Glenn ____
- Ontario's Little ______
- Ontario's neighbor
- Ontario's official bird
- Ontario's official flower
- Ontario's Old ___ William
- Ontario's Premier Ernie
- Ontario's provincial bird
- Ontario's Red ______
- Ontario's second most populous city
- Ontario's second-largest city