Biggest "bang for the buck" audio gear you have owned(in your history)?

This is very subjective, and your opinion on your own systems/items is all that really counts.

From the beginning to now, these would fit that category for me: (in no order)

Original Large Advents
Dahlquist DQ-10
Conrad Johnson ART pre.
Original Monster interconnects and speaker wires.
Nakamichi SR-3a
AR Turntable
Audio Research LS-12
Magnepan 1.6
Magnepan 20
Wireworld Gold Eclipse III
Audio Technica Electret Condenser headphones 
Magnum Dynalab Etude and 108 tuners
Magnum Dynalab Receiver (original)
And in those "early days" special pressings and imported Jazz albums. 

There may be others I am forgetting, but these were very good items along my journey. 

Bought new in 1988 Cerwin Vega D3.  They lasted forever and sounded good from day 1.  Not the best speakers in the world but a huge value for the money.
Also, Foobar2000 audio player.  Free.  Hugely customizable.  And when coupled with the $3 Foobar2000 Controller Pro app, super convenient.
3 pairs of Magnepans - 1 pair in each of the last three decades
Technics SL1200 turntable
Conrad Johnson amp
Apt Holman pre-amp 
...the multiple pairs of Walsh speaker I've diy'd.....
More time than $, but it's just another example of 'what we do for *G*'s, right? ;)
Bought a Parasound JC5 at release, owned for 2 1/2 year, sold it for nearly same price as I gave due to increase in prices. JC5 is such a remarkable amp for the money that I today own 2 x JC1+!! These cost me an arm and a leg, even tho they outperform in every way the JC5 will have a special place in my heart. It's just the best companionship I ever owned "bang for the buck" and it only cost med around $120 all inn all.

Can also mention a used JC2 I got cheap. I now run a ARC pre (the other leg and arm) with the JC+, but JC2 is actually thar good so its tucked away in 2 brand new Gant towels and stuffed under the bed as addict is to variable to temperature summer to winter. I just know to the bone that it will come handy some day..... I'm 38 years old so who knows what future brings.