" writes:
With the light switch off, but the fuse box on, if I unscrew where a
metal outdoor spotlight base meets the soffit, and grasp and pull the
base, AND if part of the base touches a wire left bare behind it,
would I be electrocuted?
As for why I'm not turning off the fuse and why there might me a bare
wire behind the base, don't ask.

Always best to pull the fuse/breaker.
But if you can't, I would do the following:
- Wear rubber/latex gloves, rubber soles (tennis shoes), use
fiberglass ladder
- Check to make sure light really is off (even with photosensor coverd
etc.)
- Tape off the light switch and put note there saying not to change it
- Make sure someone is around watching you or able to call for help if
you are hurt
- Gently unscrew fixture making sure not to touch loose wires. Don't
touch anything with your other hand.
- Use a proximity voltage sensor to touch all the wires in the box to
make sure that there is no high voltage in the box
- Confirm that voltage is *really* not present by using a voltmeter or
test light by testing between all the wires and neutral and
ground (note the proximity sensors can be fooled).
- Proceed carefully. It is always good practice to get used to not
simultaneously touching hot wires and neutral/ground at the same
time.

Note shutting the breaker/fuse is always best but even if you do,
there is always a chance that something is mislabelled or miswired
leaving live circuits within the box so the above precautions should
*always* be followed.

Admission: I typically follow only a subset of the above but I usually
know what I'm doing and I wouldn't recommend disregarding any safety
measures.

If you are not comfortable with the above or don't understand it then
call in an electrician.