I successfully made peanut butter in an electric blender while living in China. We even roasted our own peanuts in the oven (which is pretty simple) as we could only find raw peanuts in the market. Most recipes say you should supplement with oil (we used sunflower seed oil, others call for peanut oil) and a bit of salt. I added honey in ours to provide a bit of sweetness, and it also helped reduce the viscosity and mouth-puckering dryness.

It takes a little while longer in a blender compared to the proper burr grinders found in Whole foods and other grocery stores, but the end result is near identical and it means you don't have to buy a new appliance if you already have a decent blender.

A food processor will do most of what people use stand mixers for; it's a decent substitute for a meat grinder or a blender too. As "crazy large" kitchen appliances go, it's quite versatile.

I've used a tiny $19 electric coffee grinder to make sunflower seed butter. This might work for peanuts, though they are more oily.

A coffee grinder! But only use one that hasn't been used for coffee- the coffee taste will never go away. I have one I use for spices and foods, but never for coffee.