Food.
Or, to clarify, food that leaves a noticeable residue on your fingers.
If it's a piece of chocolate I can touch that with my fingers. Most dryish foods that leave little residue are okay for me to touch with my fingers.
If it's a slice of pizza or a potato chip or anything oily, I can only touch it if I know that there is soap and water readily available to wash the oil off my fingers immediately after I'm done eating it.
Anything else greasy, slimy, oily or leaving any kind of thing on my fingers, I'm averse to handling. For this reason, I don't enjoy preparing food to cook if any of the prep involves direct touching and can't be done with utensils entirely.