From reading this newsgroup and talking to people, it seems that electrical is the most feared. But there is good reason for that, since electricity can kill. I always tell people that if they are afraid of it, dont touch it, or get an education about it first.
Plumbing seems to come in second. Although plumbing is unlikely to kill anyone, it can do a lot of property damage if a pipe breaks and there is no way to shut off the flow. The bigger problem with plumbing is that the jobs regularly turn into "a can of worms". Old pipes tend to break or leak, and replacing one bad pipe often turns into replacing a lot more, ripping open walls and so on. Plumbing requires skills, proper tools, and a supply of parts on hand, or it can become a nightmare.
I'll include auto repair in this topic, and this is often a fear. Again, there are dangers involved, for example, when working under a car it must be jacked and supported properly or you can be killed. and then there is always the busted knuckles, cuts, bruises and other accidents, not to mention that one wrong move can do a lot of damage to the car. Other machines in the home, such as furnaces fall into this same category.
The other fear is anything involving heights, such as roofing. Some people are just not comfortable with ladders and heights in general. I have to admit that this is my own fear. I will work on anything electrical or do plumbing and auto repairs without fear, but I dont do well with heights.
What fears do you have regarding home repair and including auto and even small engine and other machines around the home, repairs? I think everyone has at least some fears regarding home repair....