And while I'm thinking about it, Furuya Rei is honestly a little terrifying.
If you look back, knowing who and what he is, well the first thing you notice is that he's survived undercover with the Black Organization for at least five, possibly six years. Which means he started this job when he was, at the oldest, twenty-four years old. And considering how utterly casual the Organization is about collateral damage and deaths vs how fiercely protective Rei is of his country and people, that's a phenomenal amount of stress to be under for that long.
Pursuant to which, it becomes very clear that Rei is intensely methodical. That's an interesting quality to match with his obvious intellectual brilliance and intuition, but boy howdy has he got it in spades. He tests, at every step, meticulously and thoroughly, to check his conclusions. Consider how often he appeared as scar!Akai, to Akai's allies and family, to test their responses and see if any one of them knew Akai was alive. Consider that his exposure to Mouri Kogoro started, not with the wedding case, but with the thirteen red shirts case. Rei observed Kogoro, clearly concluded that he was not going to solve this thing, and proceeded to email the right answer to him--closing with an impatient prod to hurry up and announce it so they could all get moving. And then Sleeping Kogoro puts in an appearance, which obviously gets his attention. He goes into that wedding case knowing that Kogoro is a world-class twerp, at least when he's awake, which means that Rei's own unusually aggressive insistence on his 'mistaken' deductions are a deliberate setup to push Sleeping Kogoro into another appearance, to save Kogoro's old classmate. Rei was there when the cake was stepped in, after all; given his later performances, he couldn't have missed that clue any more than Conan did. He stays close to Kogoro and, frankly, plays him like a violin, to place one test after another in his way until the tennis/dry ice case. At that point, he tests his conclusion for the last time by getting in the way of Conan's wristwatch tranquilizer. It isn't until Rei is sure of the intuitive leap he probably made by Detective's Nocturne, if not earlier, that Sleeping Kogoro is actually Conan, that he stops putting tests in Kogoro's way and starts using that lever to deflect Conan when necessary.
So we have someone with incredible discipline and self-control. Someone with Conan's (or Akai's) level of perception, intuition, knowledge, and reasoning ability, who also has the patience to test and check, to wait and see. He makes those brilliant leaps, and then proceeds to also track down his conclusions with the intellectual equivalent of persistence hunting. It's no surprise that Gin respects him, despite finding him endlessly annoying.
To be honest, if Rei weren't so impaired by his rage and grief over Hiromitsu's death, I'd bet on him over Akai, and so far Akai is the highest bar to clear, in canon.