i'll try to keep it to ten, but probably not likely. some feuds had multiple hardcore gimmick matches in them and so there'll be some extras.
in no particular order:
1. Shane McMahon vs. Steve Blackman / Big Show / Kane
any match between Shane and these guys was just insane. sure, they weren't wrestling clinics, but Shane took some major bumps in all of these and he's not even a full-time superstar. mad props for being crazy enough to do it!
2. Shane McMahon vs. Kurt Angle, King of the Ring
this one deserves a mention all its own. the suplex thru the glass was freaking sweet!
3. Angle vs. Benoit, Raw is War, Steel Cage
this is where we saw Angle's first moonsault off the cage. honorable mention for this spot goes to Angle vs. Anderson inside a cage at this year's Lockdown. but i had to give the nod to this match because it's the first one that happened and i just happen to prefer Benoit over Anderson inside the ring.
4. Undertaker vs. Mankind / Rikishi / Brock / Edge, Hell in a Cell
sure, Undertaker has been in more cell matches than these, but these are my favorites. and i know that he lost half of them. that's still besides the point. and the one with Rikishi also featured 4 other guys, but seriously, did anybody else notice them as much as Rikishi getting a chokeslam off the roof? just awesome matches thru and thru with some really good storytelling that could vary from feud to feud.
5. Undertaker vs. HBK, Hell in a Cell and Casket Match
just a great feud altogether and these two matches in particular were amazing. i loved the build up with Kane as a subplot and the following WrestleMania and Inferno matches between Taker and Kane later were just great additions.
6. Triple H vs. Jericho, Last Man Standing and Hell in a Cell
both of these were brutal matches and although Jericho lost both, they sure helped solidify him as a big time main event player that could go with the best in the most difficult matches. honorable mentions to referee Tim White that ended his career inside the cell. that's how brutal this one was.
7. Triple H vs. Cactus Jack, Street Fight and Hell in a Cell
fantastic matches. both told a really good story and Triple H actually looked like he belonged with the WHC. prior to these matches, it just wasn't that believable. his title wins prior looked like flukes. but Cactus really helped sell Triple H as a dominant heel that could win against the odds.
8. Rock vs. Mankind, I Quit Match
this was a bloody and brutal affair. i thought for sure that Mick would pull out the W in this one, but great planning by Rock to have the recording of Mick's voice screaming "I Quit" beforehand. brilliant writing thru and thru.
9. Triple H vs. HBK, Street Fight, Elimination Chamber, 3 Stages of Hell, Last Man Standing and Hell in a Cell
obviously, this was a long and bloody feud with tons of great matches from two of the all time best in the business and two of my personal favorites. great mic work and great ring work to cap off a multi-year feud.
10. Triple H vs. Ric Flair, Steel Cage and Last Man Standing Match
perfect writing for this feud. i loved the Flair win inside the Cage and the Triple H win at Last Man Standing was epic. the screwdriver was the craziest weapon i've ever seen Triple H use. totally awesome.
honorable mentions go to: HBK vs. Razor, ladder match that set the standard; Dudley Boys vs. Hardy Boyz vs. E & C in all their ladder, tables and TLC matches, all of which were crazy amazing, Mick Foley vs. Edge & Orton in their respective Hardcore Matches that were amazing and very well written, Foley vs. Flair in their semi-legit feud, etc.
tough question. i guess i'd never really thought about how many great hardcore matches there have been in the past.