I worked at a repair shop, and the worst thing I ever saw spilled on a keyboard was urine.
Urine is actually very sterile, but its acidity and yellow, that it ate through the keyboard membrane and started to seep on to the PCB.
Nothing grosses me out though. I've seen semen, blood, urine, beer, puss, spit, bile, vomit on keyboards before. I just usually grade it by how bad it ruins the keyboard.
The worst thing I ever got in the shop, though was cockroach filled XBOXs and PS3s. Those were the ****ing worst. ****ing trash from Baltimore City coming to the county wanting their garbage fixed, and they bring that trash with them.
I usually take them out back and fire bomb the unit, then if they want it back, they have to pay the extermination fee, which is $200 + the cost of the materials I had to use for the fire bomb + the cost of proper disposal of a Biohazard + HAZMAT removal of the firebomb. Which totals around somewhere near $540. They usually say no and just never come back.