I almost died on a motorcycle but somehow didn't.

Was driving a friend's bike ('79 Kawasaki KZ-1000) at night on a highway overpass and didn't realize I was doing 85 mph (speedo light was out), by the time I saw what I was doing, I was going too fast to make the turn and almost fell off of the overpass about 40-50 feet onto the interstate below. If it wasn't for the 2' high barrier, I would've died from either the fall or a car running me over. As it was, I only had bad road rash, didn't even break a bone!
When, in a sushi bar, sitting across from my boyfriend, he said yes, and let me put the engagement ring on his finger. ^.^
On christmas holiday, several friends back from college were roaming the German country side throwing large, illegal fireworks out of the car windows, scaring the farm animals. I was in the rear car when someone in the lead car threw a quarter stick out the window and it took a bad bounce, landing back in the middle of the road. Luck came into play when the driver noticed it in time and rear-ended the lead car to avoid the big boom...

Stupid things boys do with cars, beer, and explosives...
The luckiest moment in my life was when Matt had to cancel his September 11th 2001 flight to Boston due to his driving test. Not only was it lucky that he wasn't in American airspace when the first plane hit the World Trade Center, but if he had gone to America that September, he'd never have been there to call the ambulance for me.
It's a tie between the last STD test I had coming back negative, considering my ext cheated on me repeatedly and before that I had a job that was risky.

Or meeting a wonderful woman last weekend by surprise.

Unlucky on #2 is she lives in Sacramento.
Traffic Luck.
I'm going to have to go with the day I was driving my little black Subaru Justy down I5 at about 90MPH through the Terwilliger Curves, right after the first big rain of the summer. I was eighteen or nineteen. The oil was nice and slick on the road. I had just passed an accident that forced traffic down into one lane when my wheels completely lost traction and I started spinning around my own axis.

I did a complete 180, and I have a strong recollection of seeing cars rushing towards my reversed car on I5. Fortunately because traffic had been forced into one lane the cars were able to just get over into the right lanes. So none of them hit me, and somehow I didn't even hit the cement divider. I just remember my car sort of magically rolling back into a forward-facing direction, I re-started the engine, and gingerly drove off the next available exit.
Hard to pick just one. I'd say it was either the day my Mom met my step-dad (because I have had lots of opportunities that I might not have had, being raised by a single mom in rural Indiana) or every time they tell me all my tests are negative and the cancer I had four years ago is still gone.
Christmas. 2003.
Christmas. 2003. I was puppy-sitting for my mom. I wasn't participating in Christmas, but had gone with a friend to get dinner. On our way back to my mom's house, I saw John in front of his parents house loading up his car. I didn't stop then, but once at home, I called his parents. He had left, but his Mom gave me his cell phone number. I called & he said, "I'll be right over." It had been about 12 years since I saw him last and I had driven by his parents house a trillion time in those 12 years.

It was pure luck (or perhaps, fate) that at exactly the perfect time in each of our lives, I had the impetus to call, he had the impetus to come over directly, and we had the good fortune to reconnect and fall in love.
That would be when I was riding a three wheeler in southern California on a path with a super steep slope next to it leading down to a cliff. I suddenly lost control and went shooting down the hill. I seriously experienced that whole life flashing before my eyes thing. 5 feet from the cliff a root got caught on the wheel and spilled me onto the ground about 2 feet from the edge.
The day I met my wife. Friend of mine was having a birthday party that day that I really didn't want to go to. . . Not having an excuse to skip, I went, and who was there but this lovely, friendly single woman. We started talking, hit it off, and the rest is history (or our history, anyhow!).
The New Years eve, when I met the woman who has since become my wife. Everything went in my favor that night. A bunch of bizarre and humorour coincidences occurred, also in my favor.

Definately the luckiest day of my life.