Insulators crack, insulator nails work lose,wires get chewed by critters and fray, connections are brittle, terminals almost welded shut, fuses can be hard to find that are properly sized for the electrical run and boxes and runs are usually ungrounded.

In my area there are some old house with clay sewer pipe which are brittle and more prone to break or fail because of root infiltration at the joints.

Nothing high dollar but nothing cheap and brittle.

The inspector found that the Roof, that looked great from the ground, was extremely brittle. 

It is usually very brittle, but the siding on my rental is actually kind of soft and is more of an asbestoes-asphalt emulstion type material that I was not familiar with and it took me a while ot figure out it was asbestos.

We re-plumb water lines with PEX for 2 reasons: 1. lower cost, easier install, 2. no copper theft threat.Many of these properties have brass or galvanized lines, which become clogged and brittle over the years, so you'll need to have an experienced plumber if you are repairing/replacing fixtures in the kitchen or bath. 

The plastic tube that brings water to the fridge to make ice cubes became brittle, broke and water leaked all over the kitchen floor.

Vinyl does get brittle, and crack easily.  

Cast iron is brittle, you can also just smash it with a hammer.

We've been told by a couple of roofers that it's at the end of it's life and they could attempt a patch, but the shingles are so brittle that one patch might lead to another which leads to another and so on.