For me it's not actually moments, but two images stand out as all time classics.
The first was in Man of Steel Bars. Clark has just told Lois that he's leaving to go back to Smallville. He's given her his goodbye kiss and walks out of the newsroom. Before the scene fades to black we have a down shot of Lois at her desk staring at the empty spot where she last saw Clark. The almost teary eyed look of loss on her face is enough to tear your heart out.
The second is the classic scene in Just Say Noah, where Lois and Clark are in Smiley's secret office going through his notes. Lois reads his notes on them and is angered by his comments. After a heartfelt discourse about it Clark asks; "Did we just make up?" and Lois with the most adorable hurt puppy look answers "I think so.". You just want to take her in your arms. (And I would have gladly volunteered had not that stiff Clark been there).
Tank the Retired (who has a couple more images in mind but those two are the best)
