Short answer: My ranger got savaged by a wolf.
Long answer: The party was out in the wilderness without a cleric when we were attacked by a pack of wolves. My character took a lot of damage and dropped into negatives. I rolled stabilisation checks and finally stabilised on -4 hp. No more bleeding at that point though I was still badly hurt. The other PCs dressed my wounds and made me as comfortable as possible while they rested up themselves.
There is a rule that a PC has a 10% chance of waking every hour while in negative hit points. You are still pasted but now you are conscious. So, the night passed and I rolled a few checks, finally waking. All well and good. My character opened her eyes. That is all I did. The DM then called for a stabilisation check because I had moved.
I failed the check and started bleeding again. I rolled more stabilisation checks and luckily stopped at -7. I had to keep rolling to wake up and when I did I promptly started bleeding. Prior to this, the rest of the party informed the DM they were all sitting around my character's body with healing kits open and their hands literally holding bandages to my wounds. My ranger bled to -9 while I frantically made checks and the other players rolled Heal skill.
I stabilised on -9. With a night of rest I regained 3 hp (my level at the time). We repeated this excruciating procedure until I regained enough hit points to reach 0, about four days from uncertain memory as every time I woke, I started bleeding again.
We actually got the PHB out and showed the DM the rules for injured PCs but as he did not agree with the written rules, he insisted on doing it his way. This is why I say you need balance in tweaking the game mechanics. A little tailoring is fine but when you have a table of six players objecting to your rulings you should rethink your call.
The hilarious this is my 3rd level ranger survived with nary a scratch after being washed along an underground river and down a 300' waterfall.
Nihil est ab omni partum beatum.
(Nothing is an unmixed blessing)