Drjohnrock

Here's my list. Like the OP, I'm leaving out local bands. If i've seen a band/solo artist more than once I indicate that (X2, X3, etc.). I put notable (non-local) opening acts in parens after the headliner.

In non-chronological order:

Graham Nash/David Crosby (David Blue)
Kenny Rankin
Styx (Sugarloaf)
Jethro Tull (Hammersmith)
Bruce Springsteen
Bob Dylan x3 (Over The Rhine; Kenny Wayne Shepard)
Starcastle (Thom Bishop)
Ted Nugent (Foreigner, Michael Stanley Band)
Heart (The Silencers)
Stan Kenton
The Kingston Trio
Petra (first real "Christian rock" band, touring their first album)
The Band (Roger McGuinn)
Roger McGuinn x3 (as headliner)
Elvis Costello x2 (Squeeze; Talk Talk)
Jah Wobble and the Invaders of the Heart
The Damned x3 (Chivalrous Dogs)
Sonic Youth
Mission Of Burma
Black Flag
Love Tractor
Big Black
The Fall x6 (Magnapop)
Great Plains (Scrawl)
Scrawl (as headliner) x5 (Ass Ponys)
Wussy X2 (Scrawl; The Paranoid Style)
Nick Cave and the Bad Seeds (Great Plains)
Half Japanese
Half Japanese with Moe Tucker x2 (American Music Club)
Jad Fair
Mark Eitzel x3 (Jill Sobule, Rebecca Gates; Tim Easton)
firehose (Screaming Trees)
Lou Reed (The Feelies)
Rapeman
The Gun Club
The Pixies (My Dad Is Dead)
Love and Rockets (The Pixies)
The Psychedelic Furs (Our Daughter's Wedding)
The Breeders (Luscious Jackson)
Guided By Voices (The Amps)
J. Geils Band (Southside Johnny and the Ashbury Jukes)
Jackson Browne (Karla Bonoff)
Karla Bonoff (as headliner)
Karla Bonoff and Livingson Taylor
The New Barbarians (2/5ths of The Rolling Stones)
Greg Kihn
Gordon Lightfoot x2
The Replacements
The Outnumbered
Johnny Dowd (as headliner) X6 (The Scooters, Jim Roll)
Pere Ubu (Johnny Dowd)
Los Straitjackets (The Fleshtones)
Jan and Dean
Mark Russell
Webb Wilder (as headliner) X5 (Mic Harrison and the High Score)
Randy Newman
Uncle Earl (Sierra Hull and Highway 111; The Dixie Beeliners)
Sierra Hull (as headliner) X2
Jorma Kaukonen
John Sebastian
Jimmy Webb
Todd Rundgren and Utopia
Hall and Oates (Todd Rundgren)
The Guess Who (with Cummings and Bachman) (Joe Cocker)
John Fogerty (as headliner)
Peter Paul and Mary
The Jesus and Mary Chain
Spirit
Joe Ely x2 (Lucette)
Toots and the Maytals
Yellowman
Richie Havens
Gang Green
Thinking Fellers Union Local 282 (Strapping Fieldhands, Salabon Glitz)
Trans Am
Reverend Horton Heat x2 (Nashville Pussy, Backyard Tire Fire; The Creepshow)
Dead Milkmen
Live Skull
Sam Bush
Jonathan Edwards
Loudon Wainwright III x8 (Raechel Evans; Natalya Zuckerman)
Judy Collins X2
John Denver (my girlfriend bought tickets)
The Buzzcocks
Randy Newman
Al Stewart X2 (Dave Nachmanoff; The Empty Pockets)
Riders In The Sky (as headliner)
Okkervil River
Jane Siberry
Todd Snider (Mary Gauthier)
Steve Katz (ex-Blues Project, Blood Sweat & Tears, American Flyer)
Southern Culture on the Skids
Babe The Blue Ox
X_____X (Obnox)
Leon Redbone
Ralph Stanley
Lilly Hiatt (John's daughter) (Aaron Lee Tasjan)
Scott Miller x2 (Old Salt Union)
The Mountain Goats
We The Kings (a fave of my daughter)x2 (This Century, Crash The Party; AJR, She Is We, Brothers James)
Supersuckers X2(Skinny Jim and the Number 9 Blacktops; Drivin' And Cryin')*
Daniel Johnston
Hasil Adkins
Twenty One Pilots (Brand New, Shaky Graves, Manchester Orchestra, Reverend Peyton and his Big Damn Band)
Sebadoh (Qui)
Rubblebucket
Shonen Knife (CJ Ramone)
Jon Langford and Skull Orchard (Chuck and Lisa from Wussy)
Bad Luck Jonathan
Bob Log III
Buckwheat Zydeco
Rebirth Brass Band X3
Ramblin' Jack Elliott
Duke Ellington Band (after Duke's death)
Wanda Jackson x3 (Lustre Kings; Frontier Ruckus, Jonny Fritz and the In-Laws)
Steely Dan (Sam Yahel trio)
Greg Abate (jazz sax player)
Lucinda Williams (Patty Griffin)
The Stranglers
Edwyn Collins
Bruce Cockburn
Kid Congo Powers and the Pink Monkey Birds X2 (Corners, Mr. Elevator and the Brain Hotel)
Mayer Hawthorne
The Temptations (The Shirelles, The Vogues, The Coasters, Tommy Roe, Len Barry)
Suzzy Roche and Lucy Wainwright Roche (Ric Hordinski)
Barleyjuice
The Honeymoon Killers
The Beach Boys (free show after a Cincinnati Reds game)
The Cynics
The Bears
Jonathan Richman X3
Sachal Vasandani (jazz vocalist)
Tom Rush
Camera Obscura
Crystal Bowersox X2
Olivia Jean X2 (Philip Paul)
The Dickies (as headliner) (The Queers)
Muddy Waters
Dizzy Gillespie (with the Cincinnati Pops Orchestra)
Al Hirt
Don McLean
The Necros
Grand Ole Opry: Mark Willis (Del McCoury Band, Bill Anderson, Chuck Mead & His Grassy Knoll Boys, Riders In The Sky, Kate Arminger, John Conlee, Craig Campbell)
Buckle Up Festival 2014, day 2: Willie Nelson (Old Crow Medicine Show, Alison Kraus & Union Station featuring Jerry Douglas, Drive-By Truckers, Emmylou Harris)
Graham Parker X2
Chuck Prophet and The Mission Express
Calvin Johnson
The Joy Formidable
John Lodge
Brian Wilson (The Zombies)
Straight No Chaser
William Matheny
Jason Ringenburg (of Jason and The Scorchers)
Kinky Friedman X2
Song Of The Mountains TV taping: Jim Lauderdale (Sherman Holmes; Judy Marshall; Webb Wilder)
Flamin' Groovies
The Electric Six (VOLK)
VOLK (as headliner)
Flor De Toloache (female mariachi band)
Magic Beans
Social Punk Invasion Tour: TSOL (The Dickies. Total Chaos)
Dan Bern
The Nude Party (Fonteyn)
Leo Kottke
Chastity Belt
2023 Outlaw Music Festival Willie Nelson (John Fogerty, Gov't Mule, Kathleen Edwards, Particle Kid, Myron Elkins)
John Medeski (solo piano)
The Country Teasers
Buddy Guy
Jonathan Richman
Richard Lloyd