For me personally, the iron man match from 2000 was brilliant, purely because I think it soldified HHH in the main event and the fact that Taker re-debuted with a new gimmick that stuck for a few years. I think this match really pushed the idea that HHH/Rock were equals and this did wonders for both men.

Honorable mentions:
Benoit/Jericho (2000) submission match for IC belt
Put simply, 2 of the best mat wrestlers doing what they do best.

Angle/Benoit (2001)
Technically, one of the best matches I have seen on a WWF PPV and the fact that it was 2/3 falls really added a sense of finality to the match, and the fact that Angle won really gave him some heat going into KOTR and added legitimancy to Angle's amateur mat skills.

Edge/Angle (2002)
Really helped Edge break away from tag team wrestling and solidify himself as a singles star (although injury hampered this push). Also, I vividly remember cheering at the screen as Kurt was shaved, showing how over as a heel Kurt was.

JBL/Cena (2005) 'I quit' match
I think, with hindsight, this match was important to the WWE as it cemented Cena as a big player and it showed JBL ad the cowardly heel he had perfected during his 9 month reign as champ. A nice, bloody 'I quit' match, which sadly we won't see again during the PG era.

Benoit/Finlay (2006)
I never really followed WCW as a kid, so I never understood the hype over Finlay until I saw this match. These guys got a solid 20 mins to show us what they got, and this match is one of the reasons I miss brand specific PPVs ad it allows midcarders the chance to out on clinics like this.

Mysterio/Jericho (2009)
Although not a patch on their match at Extreme Rules, this match was one in a series of top notch matches between the two during 2009, and showed that Y2J could mix well with anyone, regardless of size.