For me it would have to be the Phillies and Rays last year, and the Brewers because of Braun.
I had Upton, Shields, Kazmir, Pena, J-Roll, Howard in many leagues. Also, i picked up Braun right when he got called up, and that coupled with Howard's return from injury catapulted me from 11th to 2nd in one league, eventually winning the championship.
I found myself consistently watching out for a Devil Ray/Brewer/Philly win, cause i knew i had tons of guys from those teams. It was really fun watching Tampa and Milwaukee especially with what Braun was doing.
I remember in Lincecum's first start, which i was watching on T.V. and i believe came against Philly, Howard crushed a home-run to deep center, and i was like "WOOO!!!" and then sat back down cause i felt guilty that i had put fantasy over reality...haha. But when you're a Giants fan, what's there to look forward to these days except for Barry Zito implosions and a lot of 9 - 2 nights?