Never a full attempt, but I've made many half-hearted ones that were poorly thought-out or that I backed out of due to SI.
Putting handfuls of pills in my mouth but spitting them out, trying to drown myself in the bath- And, when that failed, trying to cause dry/secondary drowning by repeatedly ducking my head underwater and inhaling- laying down on the road, sometimes even taking naps there... I often tried to use a knife, too, to stab myself or to slit my throat or wrists, but the knife was dull and I never broke skin with it, so I don't really consider those attempts at all.
I once purposefully didn't move out of the way of a speeding car when crossing a crosswalk. I suppose that might count in some way, too. Unfortunately I was with friends at the time and one pulled me away; I ended up blaming it on bad reaction time. I still mourn the opportunity sometimes, though ultimately I'm glad they didn't have to witness something grisly.