He has a chance to defeat Orochimaru (without prep)
Swordsmanship: Kakashi has shown that he can use Zabuza's sword just as good as Zabuza himself. We see him overwhelming a few of the 7 Swordsman of the Mist with the blade. And with the fact that Kakashi can infuse the sword with Raiton chakra and a Sharingan, in a sword fight, I would say Kakashi has the significant advantage. Orochimaru's Kusanagi sword is powerful and supposedly harder than diamond, but I don't see it being able to help in this situation. Despite this, Orochimaru's rebirth jutsu will come in handy, should he be bifurcated by Kakashi's blade. Oro can easily re-attach himself together the same way he did when the 4TK sliced him in half.
Taijutsu: We have never really seen any impressive taijutsu from Orochimaru. However, as indicated from his fight with 4TK, Orochimaru is skilled in using his snake jutsu in conjunction with his taijutsu for both offensive and defensive purposes. However, Kakashi has also shown that he can execute ninjutsu while evading one's taijutsu. From what I have seen, I would say Kakashi is more skilled than Sasuke in Taijutsu. Also with his Sharingan this will provide an obvious advantage in close-range combat. He also has 4.5 in taijutsu, same as Itachi. He matched Itachi's bunshin with his bunshin in taijutsu.
Ninjutsu: Now it is implied that Orochimaru knows many, many jutsu. However, as far as quantity goes, Kakashi certainly has the edge. Although Kakashi has more jutsu, the jutsu Orochimaru has displayed are very useful. His jutsu are on a much wider scale than Kakashi, and this is probably what will give Kakashi the most trouble. Triple Rashomon, that giant wall of snakes he used on 4TK, Kuchiyose no Jutsu. If Kakashi is very careful, he can take advantage of the terrain to hide his location. Kakashi always fights with Kage Bushin before he directly engages his opponent. In a forest-like setting for example, Kakashi will have plenty of areas to hide himself and distract Orochimaru with Kage Bushin. He can trick Oro into wasting large amounts of his chakra by using his more powerful jutsu on clones. Even Itachi himself cannot tell when Kakashi switches places with his clones. I highly doubt Kakashi will directly take on Oro's large-scale jutsu. He will likely use a series of Kage Bushin and hiding either underground or within the terrain to wait until Oro himself is vulnerable. Kakashi can use use Raikiri/Raiden also
Speed and Agility: We have seen Orochimaru effortlessly blitz Kabuto, and show that his speed is certainly above average. However, from what we have seen of Kakashi, I would say he certainly has the advantage in this area. Even as far back as Part 1 of Naruto, Kakashi was shown accurately reacting to Itachi's overwhelming speed. His speed has only increased since then. As far as agility, Orochimaru's rubber-like techniques helps tremendously when it comes to evading and dodging. However, we have seen Kakashi fight against Kakuzu himself, 2 disembodied Masks, and Hidan simultaneously all while protecting Ino and Chouji and not one of them were able to land a single blow on him. We've also seen that Kakashi was able to dodge a pointblank, large scale Futon from one of Kakuzu's masks while in mid-air (meaning he has no foothold to use Shunshin for dodging).
Intellect and Tactics: Orochimaru is quite obviously very intelligent both on and off the battlefield. However, there is no doubt that Kakashi is far more tactful during battle. His ability to produce accurate strategies in the heat of battle is unrivaled imo.
Why on earth should I disregard Kakashi's most powerful move?
Wrong.
Wrong again.
Kamui
Deidara has experience in fighting high level Sharingan users. He immediately acknowledged that Kakashi is using an advanced Doujutsu comparable to Itachi's.. Also don't forget that Kakashi was able to quickly absorb the entirety of Deidara's Kamikaze explosion (an attack that would have destroyed the entire forest). Kakashi's aim, speed and efficiency with Kamui has hugely increased since then. Now you could argue that when he used it on Deidara, he "missed" and only got Deidara's arm. [URL="http://www.mangareader.net/93-281-11/naruto/chapter-276.html"
]However, the only reason he missed was stated blatantly by Kakashi himself. He was unable to control the size and location of the barrier limiting the area of the jutsu. [/URL]
Since that time, Kakashi no longer has that problem. Kakashi is no longer hindered by these things. He was able to activate his MS instantaneously to blast away the Susano'o arrow sent at him by Sasuke, that too at very close range. That clearly shows his ability to warp things near instantly. Let's not forget that this is the same arrow which caught Danzo, too and would've killed him had he not had Izanagi, which effectively kept him immortal.
Also, also, he warped away a missile sent at Choji by Asura Path, when he was himself half buried in rubble. That tells you about his focus and accuracy with Kamui, getting a moving projectile so perfectly when he was at the verge of death himself.
oh, and all his feats in this war have been impressive.