This year's NCAA basketball tournament, now whittled down to the Sweet 16, has already been a good one for the underdogs. This weekend, a No. 1 seed and a No. 2 seed fell, loads of last-minute thrillers unfolded, and Virginia Commonwealth, this year's "Cinderella" team, shocked skeptics and delighted fans. Commentators outdid themselves trying to determine which upset victory was the most wow-worthy. Here, four top contenders:

1. No. 8 Butler beats No. 1 Pittsburgh
Butler, which barely lost to Duke in last year's championship game, bolstered its reputation as a "giant killer" Saturday, says Shawn S. Lealos at, handing the No. 1 seed Pittsburgh Panthers the "biggest upset" of this year's tournament. s2. No. 11 Marquette beats No. 3 Syracuse

Marquette displayed some "last-minute heroics" in their stunning 66-62 win over Syracuse, says Brian Floyd at SB Nation, but a "head-scratching" backcourt violation by Syracuse, with 52 seconds on the clock, set up the upset. That mistake allowed Marquette's Darius Johnson-Odom, who'd already scored 14 points in the game, to sink a decisive three-pointer that put the Golden Eagles over the top. (See Marquette players discuss the win)

3. No. 11 VCU beats No. 3 Purdue
In a weekend full of "shocking, last-second, upset victories, the game that likely opened everyone's eyes was the 94-76 blowout win for No. 11 seed Virginia Commonwealth over No. 3 seed Purdue," says Brad Wells at SB Nation. "Blistering" shooting from VCU, especially Bradford Burgess, and "non-existent" defense by the Boilermakers allowed the Rams to dominate. The crushing win definitely makes VCU "the Cinderella story of the tournament," says Whitney Holtzman at ESPN. The Rams barely even made it into the Big Dance, and now they're on their way to their first Sweet 16 appearance ever. (View highlights from the game)

4. No. 10 Florida State beats No. 2 Notre Dame
The Florida State Seminoles were "supposed to be overmatched Sunday by one of the best shooting teams in the nation," says Andrew Carter in the Orlando Sentinel. But they racked up point after point in their "best half of the season," and the Fighting Irish never recovered, eventually falling 71-57. To understand just how devastating this loss is for Notre Dame, the Irish were ranked among the top teams in the country before the tournament, says David Haugh in the Chicago Tribune. But they were "outshot and outworked," leading to yet another "early, inexplicable" exit for the Irish. (Watch the final minute of the game)