3.5 is pretty lethal, and I always felt it was a little weird that a sorcerer was unconscious for the same amount of time before dying as a barbarian. So I've been tinkering with the following house rule
Characters don't die from negative hit points until they reach -10 or their ECL * CON mod, whichever is higher.
I feel like it will power up the Die Hard feat, but this is ok as that feat could probably do with a buff. Is there anything else I should watch out for that this would effect and possibly break?
EDIT: Usually I use a heavily houseruled version of random ability scores, which usually results in better scores and more interesting characters. So characters start by rolling 2d6 for each ability and picking the highest. Then they roll a final 2d6, pick the highest and can replace on score with this roll. Next they roll 3d6 and drop the lowest 7 times, assign the best 6 as they want.
This has resulted in pretty good stats for PCs, with some low stats where you might not expect them. It sounds complicated, but it usually goes pretty quickly ime