Let's share some ideas!
I use the Zedge app and I do have some good ringtones, notifications and alarm music. I choose those that are rather loud since I work in a noisy environment and a run a box fan when I sleep.
(I don't know if I can embed a Zedge ringtone, but I can probably put in a link)
I've always wanted to put my ringtones as song that has the caller's name in it. I've only got like two in mind. For now I think I'll just keep the Power Rangers in Space instrumental theme as my main ringtone.
I have the Nobunaga's Ambition Theme Instrumental as my primary ringtone and my ringtone for when my wife calls is an old midi I've had since before some of you were probably born, a song called Kokoro Kimochi Kaze that I cannot find anywhere else online nowadays.
As for my notification tone? Nash from Street Fighter yelling "Sonic Boom!" :)
I used to customize my computers will kinds of sounds, but with my latest two computers I've been too lazy.
The last computer I actually modified the sound profile for I had a game-y notification for almost everything I regularly did.
Open the Web Browser? Nash from Street Fighter yelling 'Sommersault', as he would do when performing the Flash Kick.
Close the Web Browser? Nash yelling, 'Sonic Boom!'
Get an E-Mail?
Turn the Computer On? Diaz from Star Ocean 2 saying, "Piece a' Junk!"
Turn the Computer Off? Vegeta (Original) saying, "Issat enough for ya, huh? You want some more?"
At a different time I had Nash's KO grunt/echo as the sound for when I turned my computer off, too.
My buddy used to have a Waku, or whatever her name was (the red-headed mad-scientist chick from Tenchi Muyo) sound clip on his computer. When he'd close his web browser she'd say, "Oh! Looks like someone was being bad on the internet!" Always found that funny, especially when he would persist in showing me the latest hentai pictures he'd found.
I used the Castle Crashers theme for quite a while as my main ringtone. For the last few months that I had my previous phone, I went with the Peanuts theme. Right now, I'm using the Comix Zone title screen music.
As for notifications, I change it up between the Mario 1Up effect and LEEROY JEEEEENKINS! for my text messages and The Rock yelling "It doesn't matter what you think!" for emails, updates, etc.
I have downloaded many ringtones and use them as alarms, plus I like having a variety so I can set specific ringtones for specific people and change my default ringtone whenever I please. I found a few more I like.