Anyone who has the WBA 'regular' title for a start
Stiverne
Soliman
Figueroa
PEDerson
Bika
Quillin
Stuey Hall
There are others but those are the main ones for me.
I know people will say anyone who isn't a unified champion or doesn't have the ring belt is just a paper champion, but quite a lot of the current title holders are proven quality boxers.
I just recently have been watching boxing again so I can't really answer who's a paper champion. But I did research on Peter Quillin and he's the current WBO middleweight champion. Reputable publications such as The Ring Magazine don't recognize the WBO as a legitimate sanctioning body. The word "champion" nowadays is watered down but if a boxer wants to be a champion, the only recognizable alphabet soup organizations are the WBC, the WBA and the IBF. If Quillin isn't holding those aforementioned titles then it's not so much that he's a paper champion; he isn't a champion, period.
Peter Quillin
Sakio Bika
Danny Garcia
Lamont Peterson
Donaire
Bermane Stiverne.
Scott Quigg.
Stuart Hall.
Saiko Bika.
quillin is truely the only fighter I can think of, in terms of being a paper champ...I was a fan of quillin awhie back, but i'm sick of seeing him fight nobody's... he's 31-0 and only fought two decent guys Hassan N'Dam N'Jikam and king gabe rosado... (winky wright is a great fighter but was waay passed his prime when he fought quillin)
I feel like omar figueroa and leo santa cruz can step up in level of oppenents as they're champs... but wouldn't call them paper champs
I'll start the ball rolling with the most obvious: Peter Quillin! Disgraceful.