Not an exhaustive list, but I'll start with a few that come to mind that I miss:
Akordia - I wouldn't even be here if not for her player; she brought me to the game. There's a kindness to Bonnie's characters that bled in from her personality and they were always enjoyable to be around.
Krunk (I think that was how he spelled his name; was a Dwarf who helped me when I was brand new to the game) - Man, I was new and this guy got me in so much trouble, but it was always so fun to be around him. Without him I probably would have been stuck in Mithral Halls forever as he was the one that showed me the way out.
Tretch - He was the only evil Dwarf I knew of for a very long time. His character adhered to his basic tenants and, despite his evil nature, formed a bond with Selveem, Cret, and Thenwood. I miss Cret, too, even though he's still kind of around.
Seren - This guy was a good roleplayer, but always lived on the edge. With him I was always putting my characters and their gear on the line. He knew how to keep it exciting and keep me out of my comfort zone.
Teepo (though he logged recently, I haven't seen him in years) - This guy has an unforgettable character. To this day I remember him rubbing his nose!
Wynne - My first character, Gedras', unofficial wife. Wynne's player is probably
the most charitable and kind-hearted person I've ever encountered in a game. She kept Gedras down the path of being good and was also an excellent dungeon-crawling companion to Selveem.
Gwark - When Selveem met him, he was basically the undisputed King of the Orcs. Ceara (not to be confused with Ciara), Selveem's Queen, introduced him to Gwark and through Gwark fostered Selveem's understanding and care of the Orcs. To this day Selveem has an immense respect for the Orcs due to the interactions between the Ceara, Gwark, and Selveem.
OG Sune (I forgot her character names) - I was having a difficult time being new to the game and her player went out of the way on multiple occasions to help me out. As an example, Gedras fell into some pit and didn't have climb skill. He got to the point where he was thirsting and starving to death and she came to help (I think there was no pray channel back then and definitely very few Dwarves). She helped me on multiple occassions, IC and OOC, to understand the game mechanics. I was definitely a burden to her (sorry!) but she was always awesome.
Schlem - I honestly can't put my finger on why, but I miss this guy. I've never had a positive interaction with the character, but I definitely miss his presence.
Thenwood - Definition of chaos. He's quite possibly insane. Still, Tretch, Cret, Thenwood and Selveem were extremely close and I miss this guy!
Ciara - Few know this, but Selveem was extremely uncomfortable around women (still is, actually, but has learned how to hide it with some Charisma boosts) and to spite Sune, he swore off love. If there was one character that made him come close to breaking that, it was Ciara.
Rikus - Selveem met Rikus when he was still fairly young. Rikus was a fairly serious fellow like Selveem, but unlike Selveem, occasionally Rikus was definitely not. One moment in FK history I will never forget was when he and Selveem attended a wedding and Rikus discreetly lifted a cheek to break the silence. >.>
Marcus - FM of Tempus when Selveem first started out. He worked around Selveem's nature (and Orc friendship) to guide him to better serve Tempus. Every interaction I had with Marcus was enjoyable and I still remember a few of them to this day.
Garumsh - This guy kept Selveem's friendship with the Orcs fairly strong throughout his "reign." Though he never seemed to intend to become the next King of the Orcs, he was at least the caretaker of them and did his best to keep Orcs protected. Selveem respected that.
Silk (forget his character's real name; not in my logs) - Along with Xaden (Fox) and his two wives, Silk was an member of a bad group of ragtags that caused a lot of mischief in the game. My favorite was when Fox stole some valuables from a horse that had been left out in Waterdeep when it was against the rules, holed up with Silk, and then came out on his own acting as if he were negotiating for Silk for the return of the goods he'd stolen himself. >.>
Deltheric - Kiert's feigned misunderstandings and perverse nature.. Oh the fun Kiert had with this poor guy. But, it was for a good cause! Sune herself would have been happy at Kiert's matchmaking attempts!
Gorwin - This one is IC and OOC. Gorwin was always helpful and loved a good adventure. I could always count on him to be around for it, but Gorwin and his characters are such softies it's difficult not to enjoy being around them. Additionally, his alt and I created a masterpiece of a poem together!
Aldren - I've had a number of enjoyable roleplays with Aldren, but (and I know it sounds stupid,) the most memorable was when Aldren crafted the mace that Kiert used for a very long time. He still has it, by the way.
Nicholette - She holds the title of "only Sunite Selveem can stand to be around for a long time." She's extremely respectful and enjoyable to be around. It doesn't take much to get her excited about a new adventure, either. Selveem just wishes she would stop healing the scars she earned.
Zarafae - Zarafae be evil, but the best kind of evil: intelligent evil. Selveem and Zarafae were dungeon-crawling buddies. Zarafae was good about hiding her underhanded dealings from Selveem while they were together (damned devious evils) and always appeared to be an honorable person despite flawed nature in Selveem's mind.
Rhytania - She's played by an awesome player that has a lot of depth to his characters in general. Rhytania, in particular, was always fun to debate religion with for Selveem and helped him understand Tempus more fully just by listening to the way she felt about different subjects.
Danten - Another evil that was enjoyable to be around, but his player had great RPs I loved being around.
I'll probably edit to add more later and/or announce any successful reunions.

This land shall come to the God who knows the answer to War. -Ninety-Nine Nights