"Inside Track". At the start of the episode, Harvey derides Mike for wanting to celebrate with a high five, calling it basically a crude gesture especially in a public place. Later in the episode when Harvey's indy ploy works, Mike asks for a fist bump. Harvey glances into the office before smirking slightly and doing a quick fist bump.
Mike: You know you want to.
Four words: "He goes, I go."
In fact, most of the season two premiere. Harvey can't bear to fire Mike, Donna can't bear to listen to him try to fire Mike, Harvey tells Mike he's proud of him, and Harvey as noted right above, threatening to quit if Mike is fired.
In the season two summer finale Jessica echoes this when the partners are about to vote on whether to fire Harvey and she says "You go, I go." .
In "Meet the New Boss", Louis goes through a... well, I suppose his version of a Heroic BSOD, as he's discovered that his underlings think that he makes them do all of his work. Harvey, upon hearing this, is stunned, as he believes that Louis (while a dick) is probably the hardest-working lawyer at the firm. They reminisce about their days as "grunts" before Harvey remarks ("and I'm only going to say this once, so you better enjoy it") that Louis is "the man".
The look on Louis' face when he receives a tennis ball used by one of his favorite tennis stars is truly something to behold, as it's one of the few (if not only) moments where you see the Manipulative Bastard actively trying to hold back tears.
A small one when Donna gives Mike advice on how to break up with Rachel. There's a really really strong undertone that Donna's statements come from a painful and personal past experience.... and given the context, it's probably referring to the attraction she has to Harvey which crosses it over into a small Tear Jerker.
Bruno and the tennis ball. More specifically, the events that stem from it. Mike wins his first case in court and gets an autographed tennis ball for his efforts. Rachel asks for it for a reason she doesn't explain and he lets her, trusting that she's got a good reason for it. Rachel in turn gives it to Louis as a present since Bruno just died. Louis only barely manages to maintain his composure.
Mike is going to use the money from his first bonus check to buy his grandmother an apartment in Manhattan. Rachel in particular finds it extremely endearing.
Mike and Harvey get stoned and Harvey reveals some very personal information from his past. Then they decide to go to Hardman's office and urinate on his carpet.
Also the few scenes beforehand when Harvey is talking to Donna about Mike and then Harvey being at Mike's door. For starters, Harvey admits to Donna that 'he expected him to come back' and admits (indirectly) to Donna that he's come to depend on Mike as an integral part of his team as much as he's come to depend on Donna. And then, Harvey reveals to Mike that he knew about his grandmother's death and gave him work because he thought it was what Mike wanted to help keep his mind off (which Mike admits was what he wanted). It's less the actions and words (though they help), and more the tone of voice and the looks on Harvey's face. Though Mike may not have noticed, being stoned, it's clear that Harvey considers Mike as close a friend as Donna.
Mike doesn't get a bonus from the firm because no one (ie Jessica) thinks he's a lawyer even though all the other associates get one. Harvey gives Mike a bonus. Heartwarming, yes, but remember that this would also have to have come out of Harvey's personal account, so doubly so.
When Louis finds out that Rachel didn't get accepted to Harvard, he goes directly to Shiela and confronts her about Rachel not getting in. He fails to change the decision. He then goes and blames himself for her rejection, rather than tell her the brutal truth.
Louis notices Mike has just been beat up and promptly drags him to the bathroom to administer first-aid. While there, the two have a pretty personal heart-to-heart about things which builds upon the respect they had in their previous episode together. And whether it was the situation or the candidness, Louis actually almost breaks down and Mike helps him redeem himself.
Louis goes to Harvey to sincerely apologize and offer to help against Hardman in Monica Eton case against P&H. Harvey gently refuses. When Louis relents, Harvey reveals that in a deposition for said case, supposed 'facts' against Louis came up. Louis is so shaken by those facts that his hands are shaking. The heartwarming aspect comes in that Harvey supports and comforts him despite/because of all the history between them.
Last three minutes of season 2.
Mike telling Rachel "I love you" in the middle of the firm, even though they're in a Secret Relationship. Although no one was around during this, so it's not like the relationship is any less of a secret.
Louis swallows his pride and goes to Harvey for the greater good. Harvey is so impressed that he admits that genuinely respects Louis and considers himself an excellent attorney. There's even banter. Louis is this close to crying.