Rock- Hard one, but I have to lean towards heel. I think his short 2003 run was gold. As much as I loved seeing him mock and verbally tear down the heels, I enjoyed him trolling the fans even more.
Undertaker- Even though I really enjoyed his work in the Ministry, I like him more as a face overall. I loved when JR referred to him as "The Conscience of the WWE." It's awesome to see such a dark and physically intimidating guy beat down the evil heels, like Jake Roberts, Kane, Mankind, Edge, etc. Like a cross between the Grim reaper and Batman.
Austin- Definitely face, but he would have never been as over if he didn't have such a great heel run. After the double turn at Wrestlemania 13, that was first time we got to see him work as a face, and he never actually changed his character, he just beat down the heels (with the occasional stunner to faces).
*On a side note, that is why I love the Shield so much and why I feel like they are so effective as faces now. They're face turn was very seamless and they are pretty much the same characters as heels, similar to Austin.
Hulkster- What's funny about Hogan, was that even though I liked him as a kid, I was never a true fan and got really sick of him after awhile. I was a bigger fan of other faces like Savage, Warrior, Bret, and Sting in WCW. I loved when the Undertaker beat him at Survivor Series 91, I was only 9 years old at the time so that should tell you something.
I didn't really become a Hogan fan until he joined the NWO, so you can definitely say I liked him more as a heel. I'm pretty sure I'm in the minority on this one, considering I'm an older fan in my early 30s. I was never a Hulkamaniac, but I was an NWOite. Loved wearing my NWO shirt in high school.
Daniel Bryan- Face for sure. His heel work was very entertaining, and I loved seeing him play the insecure little weasel that fans would mock with the Yes chants.
Now that we see him playing the inspiring face whose spirit cannot be broken, I don't think I ever wanna see him be a heel again. His size and moves just work better as a face.
CM Punk- Just like the Rock, this one is pretty tough. I'm gonna lean towards face because I really thought his character was the most entertaining during 2011 after the pipebomb moment. It's difficult to make a choice when you take his heel runs in the Straight Edge Society days and his run with Heyman into account.
I was initially pissed when he turned on the Rock, because I thought the booking didn't make much sense at the time, although it does now in hindsight seeing how he would drop the belt to the Rock and challenge Taker's streak. I also really enjoyed his work with Heyman.
Punk's face run was awesome even though he was never truly given the chance to be the number one guy. The Nash angle was just pointless, and losing the HHH did nothing for anyone. Punk was just a guy you wanted to cheer for, and had the universal support of the crowd, unlike Cena's mixed reactions. Punk's pipebomb made feel an interest in the product, that I didn't feel since 2003. I understand Cena was still the man, but I didn't see the harm in allowing Punk to headline a few PPVs. I mean was Cena vs. Big Show for 68th time really main event worthy.
HBK- Heel for sure. I liked him the best when he first hooked up with HHH, Chyna, and Rude to form DX. I also loved his first heel turn, when he threw Jannety through Beefcake's barber shop window, then had Sherri as his manager.
I didn't like him too much during his face run in the mid 90s, and many fans felt the same way. I remember the MSG crowd at Survivor Seried 96 booing face Shawn, and cheering for Sid.
His last face run until retirement was pretty awesome though, but he was never able to top his work as a heel in my opinion. Not very many can play the cocky, arrogant douche like Shawn as effectively (that's how he was in real life at the time) while putting on 5 star matches.
HHH- Heel. I liked him as a face in DX, but he's just a natural heel. His heel run in the late 90s up until he tore his quad was my favorite run of his. I also loved him in Evolution.
Vince- Heel 100%. We had some fun seeing as a face, but his heel work is just legendary, one of the best of all-time. Who didn't want to beat the crap out of him during the Attitude era.