I've had a number of good deals over the years. Every now and then a free item pops up from a customer in an installation. A Denon DVD player, a touchpanel, an equipment rack.
But, the ones I'm really happy with are ones I paid for...
My 106" Ultimate Access V Draper Screen - over $4,000 retail, available around $3,000 online...
http://www.bhphotovideo.com/c/product/320552-REG/Draper_118291_118291_Ultimate_Access_Series_V.html
Shipped to my door for $700.
I followed up by getting a 161" version of the same thing for $300 shipped.
Second biggest score (or perhaps even bigger)...
Extron 16x8 RGBHV matrix switcher...
MSRP is about $12,000! Not joking! Online GSA pricing is about $9,500.
http://www.sigcom.net/gsaschedules/vendors/Extron LAN GSA Pricing 1-1-2002.pdf
I got it for $20. Paid $50 to have it shipped.
Otherwise, I am a dealer for several manufacturers so I always go after great promotions when available or clearances.
Got my Panasonic AE1000U projector for $250 with 25 hours on it because it was a demo model. Always a good thing!