I have most the god awful alarm clock that has that standard bell sound when it goes off. It doesn't pause and do this sound in any kind of rhythm; just an extremely loud BBBBRRRRRRIIIIIIINNNNNNNGGGGGGGGGG. It's horribly jarring; I actually stick it under a pillow to muffle it a tiny bit, because otherwise it's like a jackhammer going off next to me. But it's the one alarm clock I really trust to wake me up.
At one point, a fricking woodpecker or something drilled a hole into the side of the house RIGHT BEHIND MY BEDROOM WALL and decided to lay eggs. I like animals very much, but these stupid baby birds would start chirping for food at 5 in the morning and wouldn't stop until the afternoon. I piled pillows and blankets on top of my head, pounded on my side of the wall to try and scare them; they would not SHUT UP. We had to call animal control or something to take them away, or maybe they had already gone, but the hole was sealed and I could sleep again. Except now sometimes I hear a bird start pecking near that exact spot and I know the little SOB is trying to drill another nest behind my wall. I have to pound my fists raw on the wall to scare them away.