Uh, it's hard to pick just one so.... here's ten, forgive me!! 
1. You Debt Your Life (because of the trainwreck that is Andy D.ick,)
2. Shallow Vows
3. Tearjerker ( the Oscar Gold parody was spot on, in fact that's what I'd nicknamed 'The King's Speech' during oscar time)
4. People Vs. Martin Sugar
5. Jenny Fromdabloc
6. Francine's Flashback (for Queens Of The Stone Age being on there, which I've said too many times on here, haha)
7. Office Spaceman
8. Rapture's Delight (proving once and for all that this is the better of the MacFarlane shows)
9. Cops And Roger (the whole episode's gold, especially Roger dressing up as Russell Brand)
10. Merlot Down Dirty Shame (Roger dressed as Paul Giamatti is so funny to me it's almost ridiculous)
I <3 this show so very much. I watch way way too much of it on netflix. 