You mean Cal and Gillian, right? x)
If pretended fight counts, they fought in the episode "Life is Priceless" (1x09). They argued a bit about Zoe in "Better Half" (1x10) also Gillian was mad at Cal in "Blinded" (1x12).
In "The Core of it" (2x01) and at the begining of "Honey" (2x04) she yelled at him a bit about finances.
In "Sweet Sixteen" (2x12) they didn't actually fight but the whole situation was pretty intense. In "Exposed" (2x20) Gillian was again mad at him.
And well the first episode of third season "In the red" - Cal was really rude to Gillian.
That's all I came up with, hope it's useful :)
