Lets see.... I entered a photo of the Golden Gate Bridge at some photography contest once and won a Gitzo Series 5 Mountaineer GM5540 Monopod (retails in the $300 range I think) for free! Does that count as a sweet deal?
It's not strictly photographic equipment, but while working at a telescope store a customer wanted to get rid of a solar telescope quickly. A Coronado SolarMax 40 if anyone if familiar with those things (http://www.coronadofilters.com/products_sm40.html). It was damaged, but easily repaired. All said and done I paid $345.00, $250.00 for the scope and $95.00 for repair. Currently it is available for $1700.00 new, or about $1000.00 used.
Ok, I'll play! 2 years ago off of Craigslist, a "Cannon 3 with lens -$300"
Turned out to be an EOS 3 eye control body with a 28-70L lens and a dead battery. The guy would turn it on and it would error out. He was a realtor and bought it for home shots, but got a digital p/s instead... Sweet deal!!!
Sold the body for $350 and the lens later for $700 not a bad return!
Here's a pretty good one--I was at the flea market once, at a really junky one, this is the kind where people who clean out houses, etc., get rid of whatever is left. I saw an old camera bag and opened it up. Inside was a Contax camera and mounted on, and in pristine condition, a Zeiss 50mm 1.4. I asked him what he wanted for the camera and lens, he said I could take it for ten dollars. I haven't done too much with the Contax body (which by the way, still works fine), but have gotten quite a lot of use from the lens on my 5d2. Ten dollars; that was certainly money well spent. Only bad effect was that it really made me rue the day long ago that I had foolishly paid 300+ for the Canon 50 1.4.
I have a lot of older and rare lenses. One had eluded me for years. You only see about one a year come up for sale and usually in questionable condition. I bid on one but chickened out when the numbers increased. It went for $3k. Suddenly there was one on eBay for bid from a newbie (don't you just love Newbies?) in Hong Kong and in excellent condition. I quite bidding at $780. It finally went for $2.8K - a bargain I must admit. 2 days later I get a message from the seller that the buyer in China had backed out and since it was just too hard to relist it, would I like it for what I bid. It's mine! was my reply. And, it is in better than excellent condition.
Canon 150-600FD. At the time they were going for 4.5 to 5K. I got mine on ebay my surprise no one else bid so I got it for initial listing price which was much less. The great thing was it was a camera store selling it and they had Canon service and clean it just before they put it up for auction. I guess they listed it at a lower price expecting several bidders.
I couldn't post my best photo gear on here, since I sold the item in question (for LESS than fair market price IMO) on here.
,edit. Forgot about the 580 ex2 that I picked up from a local photog shop. Fella bought it from them, thinking it would work on his Casio (??) digital camera. It didn't work, so he sold it back to them.. I picked it up for $300, having never been mounted on a hotshoe.
Sidebar: I bought a '06 Jeep Liberty Diesel while working for Jeep. Rolled $6k neg into the finance, put 58k miles on the CRD. Sold the Jeep 1.5 years later, paid off the $6k equity, paid off the balance of the note, AND put $600 into my pocket. Aint NO WAY I expect to ever do that again!
My best deal was figuring out the time spent looking for the best deal sometimes doesn't add up to the amount saved. Now, happening onto something by chance is totally worth it.....just hasn't happened to me, yet.
A friend got a sweet deal of a near mint 1D MKII for $1700 a couple of months ago. He used it for about a month, flipped it for $2400 and bought a 1D MK III. Awesome!
I can contribute now...I looked for the last 3 months for a 50mm 1.8 Mk I, and stopped by a local pawn shop and they had one mounted to EOS 650, prices at $89.99+ TX taxes. I didn't look too closely the first time(assumed it was the Mk II) and passed up the "kit". On a whim, yesterday walked back in, and really did pay attention this time, it in fact was a Mk I. I asked when they brought it in and for how much(Oct 2008 and for $60.00), the mgr gave me 25% off, so walkout was $72.91. Probably not one of "the" best, but considering my hunt, it really was fun, and rewarding...And I'll probably end up posting the 650 on local CL...