Something that has peaked my interest lately has been ignition systems, primarily spark plugs. Picture 1= NGK Surface Discharge Racing plug. Advantage: No spark shrouding. No ground strap to build up heat in.
Disadvantage: More energy required, may not like cold starts. Expensive.
Picture 2 = Brisk Racing Silver Racing plug.
Advantage: Highest conductivity of any plug core
Disadvantage: Wears quickly. Higher cost per plug.
Picture 3 = Brisk Racing LGS type
Advantage: Heat disapation from active spark area, protruding electrode (unshrouded)
Disadvantage: multi-ground strap design can lead to inconsistent spark direction. Higher cost per plug.
Picture 4 = NGK Iridium (IX Left / OE Right)
Note the different shape of the ground electrode.
The IX is the "performance" version where the OE is just that, the long life version made for OE manufacturers.
Advantage: Availability at almost any parts store. Long service life (OE). Slightly unshrouded electrode (IX). Inexpensive.
Disadvantage: Iridium not nearly as conductive as copper or silver. If electrode tip is broken or dislodged it can cause severe damage.
Picture 5 = This is a sealing failure on an IX series plug. You can see the marks from the gas escaping. This plug has less than 5k miles on it.