I use a Coleman Ultimate Extreme 58qt cooler. It’s blue/green in color…not that it matters what color it is. 
I was wondering…what do you use?
I use a pair of the 10 gallon round rubbermaid drink coolers. You can see pictures in my gallery at www.borealbrewers.com http://www.borealbrewers.com/index.php?action=view_gallery&id=4&module=imagegallerymodule&src=%40random4a135ebf5d7d8
Coleman Extreme here too, although just the 36 quart. But hey, it is blue. Uses a simplified version of Denny’s batch sparge braid system.
I use a big orange 10 gallon round Rubbermaid cooler from Home Depot. Off-season, you can find them there for under $40.
A 10 gallon Igloo with a false bottom. It has made me many monster 5 gallon batches.
Fred
9 gallon stainless steel, false bottom, spigot. From Midwestsupplies.com
-OCD.
Gott 60 w/ 4 runs of SS braid for the manifold . . twin auto stir motors with 4 model airplane propellers doing the work.
+1 With a braid. Works great.
Coleman Xtreme 52 qt rectangular cooler w/ 12" SS braid and a Kewler Kitz spigot.
I have a 70 quart Coleman Xtreme cooler with SS hose braid. Use the following instructions: http://brewing.lustreking.com/gear/mashtun.html
Works great!
I use a 12 gallon Cube cooler with a slotted copper manifold. The geometry is good and can be safely lifted when full of a freshly doughed in mash.
I took a 15 gallon keg, cut out the top (like for a boil kettle), drilled a hole in the bottom. I welded a 1/2 inch threaded coupling over this hole, and installed a valve. Inside, I put a circular false bottom. I had to cut slots in my top opening to accommodate the screen’s installation and removal.
I built a wooden box, roughly a cube, around the keg and filled it with Great Stuff spray in insulation. When I use it, my temps only drop about one degree in an hour.
My one mistake in engineering the Mashtun was welding another coupling in the side to accept a dial thermometer. I made the hole too high, so when I’m doing a five gallon batch, the mash is actually below my thermo. >:(
used to have the 10gallon home depot rubbermaid cooler with a false bottom from morebeer. that worked very well provided that you heat it up before doughing in. now i’ve got a 1550, and with it a 15gallon stainless steel mash tun, which is good, but i think i’ll be adding some insulation on it at some point. brewing in the winter especially, i can’t imagine the temperature gradient that exists when it’s -5 outside, and 65 inside.
72 qt Coleman Extreme…Limited edition Forrest Green which means I get about 252% efficiency.
I use a converted 55 gallon drum and a chopped 55 gallon drum that holds about 35 gallon. I also have a 20 gallon converted o2 tank…
Depending on the size of the batch I am brewing I may use one of these systems or a combination of these systems
Some Pics:
I use keggles for HLT and BK.
So a Colman 70 qt extreme works for most of my brewing.
Big stuff gets the 152 quart cooler.
Both braided.
For winter indoors and 5 gal batches I have a 10 gal round gott.
Presently a bazooka tube.
Thinking about changing to a SS perf bottom.
Too much dead space that even batch sparging can’t help.
I have two of them.
One is a 10gal Orange Gott with a copper manifold. This is my primary tun which I get about 75-80% eff in. I always hit my numbers in this system so I use it the most.
The other is a 58qt Coleman Xtreme with the DC CnE setup.
I use an 8 gallon round Gott cooler with braid - got everything at my local menards many years ago. Still going strong, however, I recently converted a much larger coleman cooler so I could make bigger beers.
50 quart cube cooler with copper pipe manifold. Manifold is shaped sort of like a figure 8, with slots spaced about 1 cm apart, made using a dremmel cut-off tool. I batch sparge.
I use a 10 gallon stainless steel pot for big beers a 5 gallon pot for regular ones. Insulation did not seem to be a big problem (it cools down at around 2°F in 30 min, but I compensate for that with heating) and temperature control is very easy, because they can be heated on the stove. The 10 gallon pot I also use for boiling. During sparging there is enough time to clean the guy. I normally get 75 % efficiency.