Need an alarm.
Depends on whether or not I am enjoying my job. When I like going in, I get up about 10 minutes early. When I’m hating my job, I usually turn over and go back to sleep. And then the alarm pisses me off.
I usually wake up on my own. On the occasions I did not wake up on my own it was because I had died.
Har har… Actually, I’d get one of these but it would annoy me more than a normal alarm clock.
I use an alarm clock. However, I find that if I go to bed absolutely determined to wake up at a particular time, I will usually wake up at that time.
Alarm, but only because my circadian rhythms are completely ridiculous. I seem to be on a 26-hour cycle. I used to toss and turn for two hours every single night, until I figured out that I may as well stay up until I’m actually sleepy. Hence, I’m seldom going to bed at the right hour relative to when I have to get up.
I wake up about five minutes before the alarm about 50% of the time. However, 100% of the time I am perfectly content to roll over and grab some more sleep, so I always set the alarm.
I will sleep indefinitely if somebody or something doesn’t wake me up. At least twice I have slept for 36 hours straight and panicked when I realized it wasn’t the day or time I thought it should be when I woke up, It was very disturbing, I had sleep apnea then and it is now treated but a 16 hour sleep is still desirable now and then on the weekends.
I feel like absolute hell when I wake up no matter what. If I sit or stand still within the following 30 minutes I will fall back to sleep within seconds. It is a daily fight. OTOH, it seems to be an issue of inertia. I am a true night owl and I can stay awake for two or more days easily. My record is 3 1/2 days when I was a senior in college studying for finals. I aced all of them and then fell into a 24 hour sleep.
I have a hard time relating to other people’s sleep patterns. As a side note, I hate morning people with a passion.
Me too.
It has to be loud. It has to be annoying. Otherwise, I will wake up, but I will not get out of bed. I don’t know why.
I have little kids, hence no need for an alarm clock. There’s always a toddler jumping onto my bed and demanding breakfast two hours before I needed to wake up.
I usually wake up before the alarm, which is on the dresser right out of reach. But I set it anyhow just in case. If I sleep too long the dogs will decide they’re hungry and paw at the bed anyhow.
So to sleep late I don’t have to stay up and get drunk - the dogs do. 
I wake up 5-15 minutes before my alarm clock pretty well every morning. Even on weekends, I wake up 5-15 minutes before the alarm would have gone off. It’s most annoying.
I still set the alarm, just in case.
My sleep cycle remains stubbornly out of sync with the corporate world, so I need an alarm clock. Sometimes I need an alarm clock, sun in my eyes, and someone shaking me to the accompaniment of a brass band.
When I’m doing something that I can shift to my preferred schedule (which runs about two hours later than “business hours”), I don’t need an alarm. Also, like Shagnasty, I can remain functional for very long periods once I get going.
If undisturbed, I will sleep for 10 hours. Hence, the alarm clock. Actually, the alarm on my cell phone.
Me. If I don’t turn it on, I tend to oversleep for hours and feel awful the whole day. My body seems convinced that Earth has a 27 hour day.
I have not needed one for years and although it sits on my nightstand I don’t set it.
It is only there to tell me the time of day which can alter if my tap dancing cat decides I live in another time zone.
Depending on how much stuff I have to do in the morning before heading to work, I set it anywhere from 4:15 to 5:00. I usually start stirring around 4:10 regardless. For those 4:15 mornings I’m good to go. For the 4:40 or 5:00 mornings I roll over and snooze some more, and *that’s * when the alarm most comes in handy.
I set my alarm clock, but I usually wake up 15 minutes before it goes off.
Maybe a clocky? 
Technically, I don’t need an alarm clock, because my husband gets up before I do, and is getting ready for work in our bathroom/bedroom when my clock goes off. I still have one, though, so I can hit the snooze, and be reminded when that ten minutes is up.
I wake up with light, so , earlier in summer, groggily in winter. Usually alarm clock is set for then, and wake up before it. The cats do, too, and one likes to get up on top of me about half hour before official wake-up time, another likes to purr and get up in my face about the same time. Then the male cat, who likes to stay out all night, starts yowling at the bedroom window to come in to sleep all day. Then the cockatiels start whistling (loud) for the joy of a new day.
Muy alarm clocks here.
Should add, I often have a series of mini dreams before wake-up of the alarm ringing, and odd actions there, or, dreamlets of not getting up and getting to work on time.
Including an elaborate one of missing the subway, vivid and being in a metro area, waking up in a panic---- when I live in the country, and have an easy drive to work here. Bad, Bad, responsible worker brain for that! Anyone else’s brainpan fry them that way pre-alarm?