Many people that make these montages feel that they need to use a certain genre of music to appeal to the general crowd of gamers(Generally speaking this is harder rock/rock music, or a song like "Let the bodies hit the floor" because it pertains to what the clips are)
This may seem ideal , but I believe that just about any song could be used for a montage.
To me, its not about killing people, I dont really know how to explain it other than that, but its just not how I go about it.
Here is an example of what I think is a successful video using what could be considered a "taboo" song for a montage.
The guy who made that "Empty Productions" uses mostly that genre with his montages, more relaxed, alternative music, and I think it works very well. One think I like about it, is that the music ultimately determines the style of the video, so depending on the song/genre you use, that determines the mood that people feel while watching the video. Maybe you want them to feel relaxed(example video), or maybe you want to feel pumped up, or inspired, etc. I think the song needs to be chosen wisely depending on those factors.