(Updates at end.)
Being an electronics repair technician by trade, I have acquired a warped sense of humor and a deep mistrust of engineers (hey, if they had done their job right in the first place there would be no need for me). My experience has lead me to the following conclusions :
Electronics repair is not necessarily logical. And... Murphy was correct.
So now I present for your enjoyment the following "Murphy's Laws", at least those pertaining to electronics.
With special thanks to KB4RFP in Florida.

If anything can go wrong, it will.

A failure will not appear till a unit has passed final inspection.

Any sufficiently advanced technology is indistinguishable from magic.

The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.

Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable and three parts which are still under development.

If a project requires X components, there will be X-Y components available that is almost the same.

The most delicate component will be dropped.

Interchangeable parts won't

Components that must not and cannot be assembled improperly will be.

The construction and operating manual will be discarded with the packing material. The garbage truck will have picked it up two minutes before the mad dash to the trash can.

The necessity of making a major design change increases as assembly and wiring of the unit approach completion.

A component selected at random from a group having 99% reliability will be a member of the 1% group.

Tolerances will accumulate unidirectionally toward maximum difficulty of assembly.

The availability of a component is inversely proportional to the need for that component.

If a particular resistance is needed, that value will not be available.

Further, it cannot be developed with any available series or parallel combination.

After an instrument has been fully assembled extra components will be found on the bench.

Any wire cut to length will be too short.

Milliammeters will be connected across the power source, voltmeters in series with it.

The probability of an error in the schematic is directly proportional to the trouble it can cause.

Identical units tested under identical conditions will not be identical on final tests after being buried under other components and wiring.

A self-starting oscillator won't

A crystal oscillator will oscillate at the wrong frequency...if it oscillates.

A pnp transistor will be found to be an npn.

A fail-safe circuit will destroy others.

If a circuit cannot fail, it will.

A transistor protected by a fast-acting fuse will protect the fuse by blowing first.

Probability of failure of a component is inversely proportional to the ease of repair or replacement.

After the 24th cabinet-to-chassis screw has been removed to replace the under-the-chassis-fuse, it will be observed that the line cord plug has become disengaged from the a.c. receptacle.

After the last of 24 cabinet-to-chassis screws has been assembled, the driver tube will be found under the schematic on the bench.

The bleeder resistor will quit discharging the filter capacitors as the operator reaches into the power supply enclosure.

In an instrument or device characterized by a number of plus or minus errors, the total error will be the sum of all errors adding in the same direction.

In any given miscalculation, the fault will never be placed if more than one person is involved.

All warranty and guarantee clauses become void upon payment of final invoice.

The man who developed one of the most profound concepts of the twentieth century is practically unknown to most of us.   He is the victim of his own law.   Destined for a secure place in the engineering hall of fame, somethin went wrong.
And Murphy was an optimist !
I am sure there are many more laws attributed to Mr. Murphy. If YOU know of any, please send them to me so I can include them here.
I have found several URLs of a similar nature (Although My writings pre-date all of these):
Didier Müller in Switzerland. 
Murphy's laws on the web.

Finally after all these years, AN UPDATE!
Files this under TOOLS, not under electronics:
Lost nail clippers will be found right after you buy new ones.