Best:
Spa 1992 - Winning again in changeable conditions after qualifying (6th.. I think) in an average-at-best car and beating the almost unbeatable Williams was superb.
Barcelona 1994 - As posted above.
Spa 1995 - Started 16th after a huge qualifying crash and won the race in changing conditions.
Barcelona 1996 - Appalling conditions, pretty poor car, lapped everyone if I remember rightly. Absolutely raced away from Villeneuve.
Monaco 1997 - As Mr.Men said, won in awful conditions from Barrichello by almost a lap.
Hungaroring 1998 - Puts in fast lap after fast lap to claim an incredible win.
Spa 1999 - The move involving himself, Hakkinen and Zonta down the straight - not beneficial to him, but unforgettable nonetheless.
Suzuka 2000 - Claims the 3rd title and the domination begins.
2001-2004 : Almost everything!
A1-Ring 2003: Car catches fire during refueling, everyone panics, he drives off and wins.
Interlagos 2006 - Starts last and tears through the field to finish 4th in what at the time was his final race.
Worst:
Adelaide 1994 - Do I even need to tell you?
Jerez 1997 - Turns into Villeneuve to try and take him out as he was clearly faster, failed and DQ'd from the championship.
The 2005 season - Only win was the USA GP farce when Ferrari only raced Jordan and Minardi, struggled throughout to get anywhere near Alonso/McLaren.
Monaco 2006 - Blocks La Rascasse to stop Alonso taking pole, gets found out and shunted to the back.
2010-2012: Again, almost everything. Involved in several nasty crashes notably Abu Dhabi 2010, Singapore 2011, Barcelona 2012, Singapore 2012..
Bizarre:
Silverstone 1998 - Nobody knew what the hell was going on! Wins in the pitlane despite being given a stop/go, crosses the line to win but the stop/go wasn't taken during race distance.