Hmm, [name_m]Theodore[/name_m] is getting popular and it is better to find a name you adore if you can
Another longer dignified classic with a cute or quirky nickname:
[name_m]Thaddeus[/name_m] ([name_m]Tad[/name_m], Ted)
[name_m]Sebastian[/name_m] ([name_m]Seb[/name_m], [name_m]Baz[/name_m]/[name_m]Bas[/name_m], [name_m]Bastian[/name_m])
[name_m]Frederick[/name_m] ([name_m]Fred[/name_m], [name_u]Freddie[/name_u], [name_m]Fox[/name_m]) < any of these would be adorable with Gus
Tobias (Toby)
Solomon (Sol, Sal, Olly)
Alistair or Alisdair (Allie)
Sampson or Samson (Sammy, Sam, Sonny)
Nathaniel (Nat, Nate, Thane)
Raphael (Rafi, Rafe)
Abraham (Bram)
Phineas or Finnian (Finn)
Christopher (Kit)
Matthias (Matty, Ty)
Alexander (Sasha, Sander, Xander, Anders, Alec)
Harrison (Harry)
Other less popular classics:
George
Edward
Hector
Patrick
Hugh
Robert
Miles
Louis
Dominic
Damian
Gregory
Ivan
Alfred / Wilfred (Fred, Freddie, Alfie / Wilf)
More unusual, but still classic:
Linus
Oscar (Ozzie)
Walter
Lachlan
Lionel
Roman
Silas
Jude
Conrad
Tobin or Tobiah
Jasper
Ralph or Rafe
Abel
Roscoe
Elias
Piers / Pierce / Pearse
Amos
Iver
Isidore
Boaz
International names you may like:
Lorcan
Emrys (Remy)
Ewan
Cormac
Anders
Maxim
Soren
Ansel
Rory
Otto
Levin
Bram
Seamus
Finnian
Hamish
Eamon
Conall
Bjorn
Liev
Baptiste
Xavier
Dimitri
Wilhelm
Nicolai
Maybe an old fashioned surname name?
Jacoby
Whittaker
York
Patterson
Monroe
Ford
Orson
Grover
Blaine
Dashiell
Wilson
Sullivan (Van, Sully)
Rhodes
Avery
Hayes
Callaghan (Cal)
Ferris
Shepherd
Larkin
Redmond
Harris
Remington
Blair
Woodrow
Vaughn
Olson
Dixon
Nicholson
Rafferty
Alden
Edison
Rainer
Wilder
Jefferson
Quinlan
Lennon or Lennox
Fitzgerald (Fitz)
Baxter
Emerson
Finnegan
Barrett
Something else with an Ancient Roman feel?
Cassius (Cash)
Amias
Magnus
Atticus (Kit)
Marcus (Mars)
Maximus
Julius
Rufus
Justus
Caius
A reworked honour name:
Jameson
Seamus
Hamish
Jago
Jay
Ellison
Elan
Ellington
Ellar
Ellery
Eldin