I was just watching me some B5 yesterday. I want to say DRAAL, the Great Ham Of Epsilon III, but he was in three episodes or so, so he doesn’t count.
From the same episode that introduced DRAAL, I want to say Captain Pierce had some potential, hardass though he was. Some of his jerkassery can be chalked up to him following orders from his own higher-ups, perhaps made worse by an uppity Commander trying to overrule him (turns out the Commander in question was right about jurisdiction, since he’s the appointed commander in that sector, in addition to wearing the hat of something akin to a Military Governor).
I think Pierce (and his ship) could have been cool if they got some more screen time. To be honest, I just loved the fact that he had a cruiser with WWII style gun turrets (well, they fired plasma bolts, but you get the mental image).
The Narn who Sheridan rescued in Season 2 should count, but again, disqualified for showing up too many times (twice in Season 2, IIRC, and he became a recurring character in late Season 3). Dude was a veritable badass carrying around a sword everywhere he went, and at one point just decided he was Captain Sheridan’s bodyguard, whether Sheridan liked that or not.
“I don’t know what people back on Earth will say if I start walking around with a Narn bodyguard.”
“They will say: “Here is a man who will live to be a hundred and fifty.””