Lucas Flint (flintlocking) - Is my baby of the bunch and is willing to talk to pretty much everyone for whatever reason. His elder siblings are Slytherins so basically Lucas is immune to people trying to give him the brush off/be snarky. He wants to make friends with everyone so I'm sorry, Blaise doesn't have much of a choice.
Daisy Potter (this journal) - She's two years younger than Blaise and in the same house. Daisy is decent friends with Draco (if only to make Harry twitch) and Millie. She would be willing to make friends with Blaise as well. Totally depends if Blaise wants to, however.
Persephone Rosier (primandproperly) - She and Blaise were sorted in the same year, though by some strange twist of fate (aka me, the player) she got sorted into Hufflepuff instead of Slytherin. So second only to Ally's Zacharias is she the most unlikely Hufflepuff ever. She and Blaise could be friendly, I think. She very much likes aesthetically pleasing things, only she tends to like things that could also kill you. But that's neither here nor there. Technically she works in the Department of International Cooperation, but officially under the International Confederation of Wizards to help track down dark objects. I look forward to their interaction.
Peregrine Troy (pipsqueak) - He is a quidditch player and several years older than Blaise. They probably wouldn't know one another, but random interactions in the future are always fun.
Percy Weasley (arulefollower) - He's probably a lot like you remember in the books, only not quite. He's still pompous, dry, and pretentious, but that is generally moderated by the fact that he's utterly in love with his wife and she has helped him loosen up significantly. He works for the Department of Games and Sports and knows far too many Quidditch statistics. They both work in the Ministry so they at least have a chance of running into one another?