This is a pretty hard one for me really, and it doesn't help that my musical interests are insanely varied. Right now though the three groups I'd say that are vying for "favourite band" are Linkin Park (I see I'm joining a bandwagon on this one), Nightiwsh and Insane Clown Posse (if you can count two rappers in clown make up as a band...). Before people throw a lot of "lolwhat" at me I thought maybe I'd put in some explanations below.
1. Linkin Park - This band are incredibly versatile, incredibly talented and constantly produce top-quality and meaningful music. Chester is arguably the most talented male vocalist around at the moment being able to scream like a demon one minute and sing like an angel the next. I will admit that he hasn't got the screaming lungs he used to but he's still very talented. Mike too, is a great vocalist. He isn't necessarily as good as Chester, but his raps generally have a very good flow to them and when he sings it is generally of a very high quality, I don't think he has a great range though compared to others. I would take the time to comment on every member individually, but yeah screw that. Bottom line is, very talented + very meaningful songs + versatility= awesomeness that can appeal to a wide range of audiences.
2. Nightwish - You wouldn't think it would work is you heard someone on the street go "It's like opera and metal. Together" but the fact is Nightwish are incredible. More or less one of the pioneers of Symphonic Metal (which is basically the marriage of metal and operatic elements) as I understand it they're songs were always deep and always beautiful. Tarja was a better vocalist for the band then Anette I must say (I am yet to hear them with Floor) but both are top-quality singers and Toumas is a musical genius.
3. ICP - Here is where pretty much everyone on Earth will probably disagree with me. But quite frankly, I love Horrorcore. I'm not a crazed juggalo fanatic like some I guess but this group have great flow for the most part (essential for rappers), excellent lyrics and incredible theatrics. When you add this to the fact that behind all the violent supernatural themes in the music there's actually a pretty deep spiritual philosophy that nobody bothers to look at, need I say more. I get that this is a "love them or hate them" kind of group but I definitely am in the love them category.
For those who don't know - Horrorcore = Rap vocals with strong heavy metal influences and a focus on violent/supernatural themes in the lyrics. Although there is a lot more too it.
Honourable mention right now can go to Black Veil Brides, Imagine Dragons and Of Monsters and Men.