I use the music for the "eye catches" that the anime show Azumanga Daioh used going into and coming back from commercials (the linked YouTube video has both the going and and coming music; on my devices, I have these as two separate alarms that I alternate between) (also, this video cuts off the first few notes of the going theme when it first loads, but if you rewind to the beginning, it plays the whole thing).
I want an alarm that will wake me up without pissing me off. If I have to wake up to a jarring sound like the standard "buzzer" alarms I will be angry all day. My alarm of choice uses the 3rd and 4th movements of the William Tell Overture. The 3rd movement is peaceful and gradually gets louder until the 4th movement starts (think the Lone Ranger) and if I'm not up by then it's my own fault.
Fairy fountain from the Samsung devices. Quiet enough not to put me in a bad mood, but the running water makes sure I don't just want to get up, I have to.
I just use the default alarm sound on my phone with the briefing alarm that speaks the weather and my agenda which is rather twisted and morbid because the news usually talks about a train wreck or a terrorist attack and then it plays that joyous song right after. Wakes me up laughing.
I have a free tunes I vary between, mostly video game songs. They're all calm enough. A couple tunes from chrono trigger (peaceful days), a couple wild arms (wild arms 1, opening) and the ocarina of time kokiri forest tune. Then there's back in time by Huey Lewis - all are zedge