Nico briefly ships Victor and Lillie, a New York girl from the 1800s. Pretty much all of the earlier Runaways shipped Gert and Chase.
Molly seemed to ship Xavin and Karolina first. The other Runaways seemed to join her once they realized that Xavin really wasn't going to kidnap or enslave Karolina.
During a period in The Nineties when Lois and Clark had split up, Mr. Mxyzptlk of all people, tried to push them back together. Being an annoying trickster, this was not appreciated and he was firmly told that they'd resolve their problems in their own time.
This was one of Harley Quinn's schticks in her solo comic series - every once in a while she would latch onto a budding couple and become obsessed with bringing them together. She always succeeded, but since her methods for bringing together include kidnapping, armed robbery, shootouts and blackmail, the journey wasn't always great for the people she helped get together. And if you got in the way of what she saw as true love, it could prove a costly - even fatal - mistake, though she may not always be aware she killed you...
Peanuts: Sally Brown usually doesn't seem to care much about her older brother's happiness, with one notable exception: She will encourage any hint of romance between Charlie Brown and Marcie.
In Spider-Man Aunt May always was very vocal about wanting Peter to end up with Mary Jane Watson. You could say that May started out as The Matchmaker, as she and MJ's Aunt Anna set up Peter and MJ's first blind date and at the time Stan Lee did not yet intend Peter and MJ to become the Official Couple. When they finally did, during the original Clone Saga, May Parker gave Mary Jane a pep talk to fight for her man when Gwen Stacy apparently returned from the dead.
Although Roger Stern has gone on record as disliking the Watson-Parker romance, when he brought back Mary Jane to Peter's life in Amazing Spider-Man #242 as "just a friend", he immediately showed Aunt May, Aunt Anna, Peter's first love Betty and her husband Ned Leeds, and Liz Osborn all doing their best to bring the two back together as a couple. Peter (then busy with his romance with the Black Cat) and Mary Jane reacted with a mixture of annoyance and amusement, but what do you know? Not that long after they did get back together and four years after MJ's return they got married.
In Ultimate Spider-Man, Gwen Stacy supported Peter and Mary Jane, proving MJ's insecurities about Gwen and Peter's relationship to be unfounded.
In Scott Pilgrim, Scott's roommate Wallace seems to be fond of Scott/Ramona.
Star Sapphire Mirri Riam ships Kyle Rayner and Soranik Natu. This was fine for a while, but when they broke up it goes badly. She was so dedicated to her OTP that she ravaged a planet to force them to work together and rekindle their romance. When she told Kyle and Soranik her reasons they understandably thought she was insane.
Another X-Men example, in X-Men: First Class Iceman (Bobby Drake) and his then Heterosexual Life Partner Beast (Henry "Hank" McCoy) actually debated who they believed Jean Grey should be shipped with, or at least who she shipped herself with. Beast believed Jean liked Warren Worthington III/Angel, while Iceman believed (correctly) that she preferred Scott Summers/Cyclops.
In Marvel's The Mighty Thor Thor's dad Odin shipped - and probably continues to ship - Thor with Sif, to the point that he set up a contest to prove to Thor that his mortal love interest, Jane Foster, simply couldn't keep up with the pantheon of Norse gods and goddesses.
A few people are this for Katchoo and Francine at various points in Strangers in Paradise; the moment where David and Casey handcuff the two together to hash out their differences is probably the most extreme occasion.
In New X-Men: Academy X, once Hellion finds out his teammate Mercury has a crush on Wither, he immediately becomes very supportive of it (despite distrusting Wither seconds ago), and even makes a few subtle moves to encourage Wither to return her feelings.