Quite dificult to narrow it down to 10....
These aren't necessarily in any order, just 10 favourites of mine:
1: Mankind VS. The Rock - "I Quit" Match - Royal Rumble 1999
I wish I watched wrestling during the Attitude era but alas, I just missed it.

Just a brutal match, with Foley taking most of the abuse (obviously). The unplanned ending where The Rock whacks Foley with the chair ten times really made Rock look evil and Foley as nearly indestructible. Also, some great one-liners on the mic. ("The Rock's gonna kick your fat ass...") The best (only?) match to manage to mix senseless violence and comedy.

2: Randy Orton VS. Cactus Jack - No Holds Barred Match - Backlash 2004
Foley countering the RKO by dumping Orton onto the tacks is just a brilliant moment. Orton sold everything in this match really well and took quite a few bumps (the tacks, being thrown off the stage, the elbow drop off the stage). Lawler's support of Orton during the match and his criticism of Foley I enjoyed too. RIP heel announcers.
3: The Rock VS. Stone Cold Steve Austin - Wrestlemania 19
WM 19 is my favourite WWE PPV and this match is one of the reaons why. At the time I didn't know that Austin was planning on retiring from the ring so I don't think I knew who was gonna win. I liked the atmosphere of the PPV, what with the semi-open stadium and the fact the crowd looked even bigger than it probably was. My favourite of their WM matches, and surely the best note on which Austin could have ended his in-ring career (than God that Syber Sunday match with The Coach never happened...

).
4: Kurt Angle VS. Brock Lesnar - Wrestlemania 19
The only real 'wrestling' match on this list.

I guess a classic match is to be expected when you put two guys with 'proper' wrestling backgrounds in the ring. It may end up being forever remembered for Brock's Shooting Star
Botch Press ("Oh my god, how is Lesnar not dead right now?!" - Tazz) but the reast of the match before that was excellent.
5: Hulk Hogan VS. Vince McMahon - Street Fight - Wrestlemania 19
Yet another reason to love WM 19.

The idea of two middle-aged men who weren't competing in the ring regularly having a match at Wrestlemania shouldn't really have worked. But the Street Fight rule allowed them to do all sorts of stuff, including a Vince leg drop from a ladder!

Madness! Vince's "here's Johnny"" look when he looks over the ring apron is classic too.

6: Mankind VS. The Rock - Last Man Standing Match - IYH: St. Valentine's Day Massacre
OK, there
was another match that managed to mix senselss violence and comedy. A month after the "I Quit" Match, Rock and Mankind's rematch was a Last Man Standing Match in which The Rock performed a rendition of Smackdown Hotel.

The ending (with both guys knocking each other out with chairs) may have disappointed people but worth it to see Rock nearly fall out the ring after being hit in the head. These two have definitely been involved in some of the great WWE matches over the years.
7: Elimination Chamber Match - Survivor Series 2002
Just because it was a new concept and it was Shawn Michaels' second match in over four years. There isn't really one reason I can come up with for I enjoy this match, I guess I just do.

8: Mankind VS. The Undertaker - Boiler Room Brawl - Summerslam 1996
Despite the fact that the camera signal cuts out a few times and the announcers barely speak during the time the two guys are in the boiler room, I still really like this match. I think maybe the lack of commentary and the 'sloppiness' of it makes it seem more real. There aren't really any obvious choreogrpahed spots (except for maybe Foley being tipped off a ladder onto a pile of boxes) either, which helps since there's less chance of something going wrong. The Paul Bearer heel turn at the end was done well too I think. Extra points for Paul's post-match "I'm Paul Bearer and you're not!" comment to the camera.

9: Armageddon Hell In A Cell Match - Armageddon 2000
Again, like the Elimination Chamber, it had six guys fighting, though in this one, they were all in the match at once and the fight ended up at the entrance way. Nothing technical really, just a sort of wonderful chaos.
10: Brock Lesnar VS. The Undertaker - No Mercy 2003
This one may seem like an odd choice amongst all these famous matches but I've always really like this match. It was a Biker Chain Match, but the chain only came into play right at the end when Lesnar wrapped it around his fist and nailed 'Taker with it. Brock was in his second heel phase and Bikertaker was still alive. A very good mix of wrestling and brawling IMO. The announcers did a good job of selling the match and each guy's moves etc. Besides a UT piledriver on the steps where Brock's head clearly doesn't conenct with anything (unlike the WM 19 Shooting Star Press, HIYO), it was just an overall well-done match.
Honourable mentions to HBK/Diesel at IHY: Good Friends, Better Enemies, the various TLC/Triangle Ladder Matches invoving the Hardys, Dudleys and E&C, HHH/Foley at Royal Rumble 2000, Kane/Shane at Survivor Series 2003 and the
**** Triple Threat Match at WM 17.