My pair of choice? The delectable MomoChissa pairing:
It's not a common pairing, given that they're in different groups. It was difficult looking for photos of them together, that's for sure.
Given that their primary interaction would be in the Hello Project concerts, they've still got quite a lot of interactions between them. Chissa's also a massive Buono! fan, so she supports them indirectly.
There was the time when they were looking to form a new unit with the Elder Club after Nacchi and Maimi performed together:
Well, Momo's idea, but Chissa let herself be dragged along.
Momo also popped up in an episode of Okai-chan Neru, which had both of them outdoors. There was a mini live session with both of them singing Buono! songs. And Momo attempting to persuade Chissa to change her favourite Buono! song from Shousitsuten Vanishing Point to I Need You.
In one of the H!P questionnaires, Chissa also mentioned that if she could form a unit, it would include Momo (specifically, Momo, Yuuka, and Takahashi Ai). Momo's own entry had 'recruiting members'.
I guess it seems a bit one-sided since Chissa mentions Momo more than Momo herself reciprocates. Come to think of it, Momo doesn't really talk too much about her interactions with the others - she tends to talk about her family instead. I don't think she's mentioned Mano much wither, although they seem to be good friends - before one of Mano's lives, she and Momo started drawing Pokemon on the whiteboard.
On a tangent, during the Nico Nico Sakura-con interview with Berryz, Momo mentioned that her favourite Pokemon was Pikachu. I would've guessed Jigglypuff, but I guess I was wrong. Either that, or she wasn't sure that most people wouldn't know Jigglypuff's Japanese name, Purin. Which is where the name of this blog comes from, incidentally.