This is another one of those house rules that have lived in my mind forever, but I always forget to write down:
you can take Vulnerability x1.5 for half the cost of Vulnerability x2. I most often use this for crushing damage on things like birds and skeletal undead. Double damage from crushing is usually too much, but crushing at x1.5 is threatening without getting the target crippled anytime a blow lands and matches cutting damage
I don't remember if I came up with this number myself, but its useful, and it stuck.
Related side note: I also like to treat vulnerability x4 damage as actually being x5, mostly to make the progression follow the size/range table.
I hope people find this useful, I've been trying to actually write down the house rules I use. Happy Gaming!
