When thinking about an Entourage fic to rec The Heartbreak Kid by Astolat is the first that comes to mind. It's not that I don't love pretty much every Entourage fic I've found, just like I love Entourage beyond reasoning, but there's something really charming about this story that makes me grin each and every time I've read it. (I'm also not sure it's my favourite of every story by Astolat/Shallot because I've yet to read something she's written that I haven't enjoyed.)
So this story starts with Vince seducing E on a whim and then Eric runs away. It's got great characterisation, fantastic banter and most importantly it hits all the right spots.