Hatake Sakumo
Also known as the "the great white fang", Kakashi's father was a reknowned ninja for being on the same level as the Sannins. Unforunately, due to the tragic outcome of a mission, Sakumo was disgraced and eventually took his own life.

Yondaime [ Fourth Hokage ]
The only surviving people in Konoha who knew the Fourth Hokage the best would be Jiraiya and Kakashi. Considering that Kakashi was trained under the Fourth Hokage, the way he sees him as a person would be much different than the others in the village.

Sandaime [ Third Hokage ]
There hasn't' been any direct interaction between the Third Hokage and Kakashi, however it seems as if the Third Hokage is quite familiar with him. Although Kakashi has never passed any Genin exam students, the Third Hokage trusts his judgement.

Orochimaru
It seems as if Orochimaru is quite familiar with Kakashi's past for he knew that the Sharingan was something he sought for. It is unclear how familiar they are with each other, however Kakashi does have some repect for Orochimaru being one of the three Legendary Ninjas of Konoha although he is an exiled ninja. During the Chuunin exam Kakashi claimed that it would be alright to kill Orochimaru for what he's done, however with just simple words, Orochimaru proved him wrong.

Jiraiya
It seems as if Kakashi had known Jiraiya in the past because he was suprised to see him back in the village. Naruto was not originally under Jiraiya's tutelage but rather under Eibisu's tutelage. However due to unfortunate circumstances on Eibsu's part, Jiraiya took over.

Tsunade
Tsunade is another of the Three Legendary Ninjas of Konoha. Like Jiraiya and Orochimaru, Tsunade also knew Kakashi before she left the village. Not much is known about their relationship, however Tsunade seems to repect Kakashi for being a genius ninja.

Obito
Also known as Kakashi's late best friend who was killed while on duty. Obito's death surely impacts how Kakashi currently interacts in the story compared to how he would have acted before because it is known that whenever he visits the memorial, all he can think about is all the foolish things he had done in the past. Obito is the one who gave Kakashi his sharingan.

Rin
Rin is the medical ninja in Kakashi's team while he was under the supervision of Yondaime. She was also the one who transplated Obito's eye for Kakashi.

Maito Gai
Gai sees Kakashi as his ultimate rival. It's like the way his student, Rock Lee, determines his rivals Gai is trying to prove that there is little or no difference between those who are geniuses and those who work hard. Kakashi seems to be indifferent or give little interest towards his and Gai's rivalry. Their competitions include counting the amount of people they've defeated during the Konoha raid which occured during the Chuunin exam, and in games such as Rock, Paper, Scissors. Gai has also formulated a way to defeat Sharingan users by predicting the opponent's next move by watching their feet.

Umino Iruka
Naruto, Sasuke, and Sakura's teacher while they were attending the Ninja Academy. Iruka first objected the idea that his students being entered in the Chuunin examination shortly after graduating from the Academy, however the results of the exam proved him wrong. Kakashi and Iruka do not interact much other than arguing why the current Genins are worthy of taking the Chuunin exam, however Iruka does have respect for Kakashi for being a higher ranked ninja.

Sarutobi Asuma
Like Kakashi, Asuma is a laid back Jounin instructor. There was a scene where Kakashi saw both Kurenai and Asuma walking together and he questioned their motives of whether or not they were dating, however it seems as if Asuma is just another one of Kakashi's acquaintances.

Yuuhi Kurenai
Kurenai has recently been promoted to Jounin rank right before the story of Naruto started. Being a new Jounin, she wasn't familiar with the other Jounin's tendencies, for example Ibiki, however she does have great repsect for Kakashi. Like Asuma, Kakashi most likey sees her as a acquaintance.

Ebisu
Known to be a private elite Jounin tutor or, according to Naruto, the "Closet Pevert". Shortly after completing the preliminary round in the Chuunin exam, Kakashi asked Ebisu to tutor Naruto so he could teach him how to refine his chakra molding techniques. If it weren't for Kakashi's request Ebisu would probably have never considered tutoring Naruto. Ebisu was also Konohomaru's tutor before he entered the Ninja Academy.

ANBU woman
This unnamed woman most likely had close ties with Hayate, the Chuunin examiner who looks half dead. During the Third Hokage's funeral, the ANBU woman ran into Kakashi at the memorial and it seemed as if they've known each other in the past. Perhaps they knew each other when Kakashi was in ANBU.

Morino Ibiki
Ibiki is the Captain of the Leaf Assination Interroation and Torture Unit. Kakashi is familiar with the ways Ibiki interrogates his victimes most likely due to him previously being part of ANBU.

Kabuto - A Genin who failed the Chuunin exam a few too many times. Adopted by a member of the ANBU medical team, Kabuto is quite familiar with medical jutsu. According to Orochimaru, Kabuto is about as strong as Kakashi. Kabuto has also found Kakashi's weakness in his blind spot while Kakashi was fighting him in the hospital.

Uchiha Itachi
Kakashi most likely met Itachi while they were part of ANBU because while they were fighting they seem to be quite familiar with each other. The reason which may be the reason why Itachi spared Kakashi's life during the Tsukiyomi would be out of respect for a person of non-Uchiha blood to use a Sharingan so well.