Luke Gallows' theme is actually very very old. Big Show used it when he first came to the old WWF in attitude era. And it doesn't match his gimmick at all. Last time I checked, Staight Edge was about Punk Rock, not weird rap beats.
Actually Straight Edge is about no drugs, sex, alcohol, or cigarettes... Choice of music has nothing to do with it... And Kill Switch Engaged is NOT Punk Rock. They're Metal, learn your stuff
As for theme songs, I have to admit that at times they annoy me... however, within recent times, they haven't bothered me much except for Cody Rhodes. Yes, he needed a change but his new song sucks.
Changes that I truly like are...
Nexus - From using their Pros themes to using "We are One" by 12 Stones, I think this song fits the group entirely. It shows how they connect and prevail all the time, each and every time.
Evan Bourne - Don't know if people remember much, but Evan Bourne used to come out to a very lame theme song... Now his "Born to win" theme is amazing, and I love the lyrics in it... although Bourne doesn't win much, it's still pretty kick ass.
Drew McIntyre - Don't get me wrong, his old theme was good. For a generic wrestler, his theme fit perfectly... But when he was crowned the "McMahon's Crowned Jewel" then he needed a theme change. And with how he tormented Long, Hardy, and Kingston I would say "Broken Dreams" have fit him perfectly.
Ones I don't approve of...
Kane - I HATE HATE HATE his current theme song. I personally think that Slow Chemical was his best theme song, although it doesn't fit him anymore. I would love to see him go back to his oldest theme song though, I loved that one too... like cream my pants love
Rey Mysterio - I loved his original theme song, and still bang it in my car every now and again
Cody Rhodes - I said it earlier, he needed a new song, but this isn't it. I personally think that Johnston could've come up with something better.
Cena - My time is now is old... I would love to see him come out with "Bad Man"
And here's some that I think, or want, to have theirs changed.
Khali - Because I'm really going to be terrified of a 7ft ****** who comes out to Punjabi Porn music.
Jillian Hall - Give it a Techno Remix, and it'll go over well in the arena.
Gail Kim - I hate her period... but I'd hate her less if she'd change that song (and fix her face).
Kelly Kelly - Makes no sense to me...