Its awesome when Fitch gets the timing right and and enters the cage exactly when the beat changes in Rusty cage by johnny cash.
For some reason Kick in the door by Biggie seems like a Perfect match for Frankie edgard
And of course sandstorm, Hate the song. But love it every time wand walks in to it.
Unused: the Best around (karate kid theme) should have been used by Machida.
The trooper by maiden is a great walk in song too.
Worst has to be any non catchy rap or heavy metal song no one has heard before. But if it fires up the fighter so I can watch a great fight I'm all for it. 
Rashad coming out to KRS at 108 and Mobb Deep against Page had me pumped as fuck
http://www.youtube.com/watch?v=4R-XdOaDho0
Dont know why no British fighters rep some real Dizze rascal
http://www.youtube.com/watch?v=DjGVAwyb454
Santino DeFranco - I always thought O' Fortuna would be a great song to come out to, however, it would have to be edited to exclude the first :25 seconds as that is the beginning of the horrible UFC intro (before the guitars/metal stuff)
Marquart comes out to that sometimes.
Samsonite1084 - If you want blood, you got it by ac/dc <img src="/images/phone/apple.png" alt="Phone Post" border="0" style="vertical-align:middle;"/>
Dammit, u beat me to it. I haven't heard anyone come out to that one.
Unused, I Think
Metallica's "For Whom the Bell Tolls" and "Seek and destroy"
Five finger death punch's "BAd Company"
Motorhead's "Ace of Spades"
Marvin Hagler's walkout song: http://www.youtube.com/watch?v=TZHIo5ylQA8
Has anyone walked out to these songs?
Someone needs to walk out to this song. Not big on Dubstep, but this song is raw. To me it has more in common with metal than electronic music.
Blue please
"Machine Gun (16Bit Remix)" by Noisia
http://www.youtube.com/watch?v=_Waqn0jBG58&feature=youtube_gdata_player
...best eva would be...ANGER by DOWNSET
Bobby Lupo - Dan Miller has hillbilly music and he's from Jersey.
If you were ever in Sussex County (where Miller is from in NJ), you would understand why he uses hillbilly music.
High Point (the best wrestling team in Sussex County) has this on their t-shirts:
The whole damn state isn't "Jersey Shore".
Crashing Around You by Machine Head would be a good one as well. 
I also think early Gravediggaz would be good.
Suicide, diary of a madman, or bang your head, although there would need to be a lot of editing for f bombs.
I love BJs music
Brocks enter sandman is BA
As well as Diaz coming out to deftones
Not sure if it has been mentioned but when the napsack Clay Guida came out to Refused's song New Noise is my all time favorite.
Who was it that came out to Bro Hymn by pennywise recently? That was rad as fuck!!
bigbenpie - Who was it that came out to Bro Hymn by pennywise recently? That was rad as fuck!!
Jason Brilz always uses it.
My favorites:
Gil coming out to The Beast
Tito using Mosh (although I'm warming up to Cinderella Man)
Lunatic Fringe
Country Boy Can Survive
For Those About To Rock (I can't believe this is the first mention!)
Con Te Partiro. Classic.
Fedors new song. Love the almost haunting tone in the guys voice. It fits him well.
Most underrated: Kaplan coming out to "Tenderness" by General Public at the TUF 8 finale.
Worst:
Monson using "Imagine" by Lennon.
Siver using Last Resort.
Anyone who uses Nickelback.
TheBigBadBootyDaddy -Shame that it isn't.Bobby Lupo - Dan Miller has hillbilly music and he's from Jersey.
If you were ever in Sussex County (where Miller is from in NJ), you would understand why he uses hillbilly music.
High Point (the best wrestling team in Sussex County) has this on their t-shirts:
The whold damn state isn't "Jersey Shore".
Another one I forgot for best:
"Too Much Fun" for Chael
TOOL - EULOGY
Perfect lyrics for GSP against Diaz
Sorry if this has already been posted. Here's Nick Diaz perfect walk out song!
The best walkout OF ALL TIME is when Joseph benavides came out to james brown "payback" when he fought Cruz the second time and anytime nakamura comes out to time to say goodbye
maxbrothersinc - Best:
Fedor entrance: Era - Enae Volare Mezzo
Unused:
Trooper - Iron Maiden
Running up that hill - Placebo
Worst:
Any eminem song
Frank Mir: Amazing - Kanye West
Swag