New to the concept of a rattle gun.

Can anyone suggest a good brand?
How large a compressor, and what pressure do they need to run?
Are they adjustable for torque, ie do they have a setting for say 150 Nm or just numbers 1 to 4, and you are basically guessing at the torque they put out? How accurate is the torque setting? Anyone done up wheel nuts and checked accuracy with a torque wrench?

Like I said, nOOb questions!

Just discovered they also come in 240V, 12V and cordless versions. Anyone used one of these?

Your average compressor will work fine but often can't pump fast enough with a $100-$250 compressor to make it super fast to say, undo your entire cars worth of wheel nuts.. you'll have to stop and wait for the pressure to build a few times... so consider a larger tank with a faster pump. Also consider an electric rattle as the cost of that can compare up to a good compressor and rattle set.

You can pick up rattles in air tool sets for about $100, you can get a slightly better one in the $100-$200 range - also remember you'll need an impact socket set which you can also pick up a reasonable one for about $100.

dont rely on the torque settings at all!!!!! basically ure only changing speed not torque... depends on ure budget but try and go with a reputable brand... Ive brought air tools no name or Chepos before and haven't last 1 week so.....
the electric guns are good but expect to pay $500ish and they're not as powerful.

my 2c.
2.5HP 40L? air compressor from supercheap with one of there rattle guns (cheap ones) undid 2 wheel nuts from 5. had NO GUTS whatsoever. Decided to just look for a tyre lever.

So just steer clear of the 2.5HP compressors :)

Hrm I have a mate with a $250 compressor and a $100 air tools kit rattle gun and it undoes all of mine. Problem is you have to wait for the pressure to build back up.

Also make sure you keep oiling it!

Also if you break them when on the ground it'l make it faster to wind them all off and back on

Yeah strange. Couldnt find my wheel nut undoer thingamabob, so yeah it fails at undoing wheel nuts if they havent been cracked.

dont rely on the torque settings at all!!!!! basically ure only changing speed not torque... depends on ure budget but try and go with a reputable brand... Ive brought air tools no name or Chepos before and haven't last 1 week so.....
the electric guns are good but expect to pay $500ish and they're not as powerful.

I took a chance on a taiwanese brand called JTC (jetway tool company) which set me back $105AUD for this model

http://eng.jtc.com.tw/Archive/products/3202a.jpg
http://eng.jtc.com.tw/products/products_show.php?pid=1180&cid=190

Wasn't expecting much out of it but boy was I wrong. I've had the tool for about 3 years now and its not skipped a beat. Gets used every day and its the one everyone else in the workshop goes looking for\comes to borrow when a wheel won't come off, or a crank bolt needs to come out but won't etc. And the others bought Blue Point, Hazet, Wurth, SP Air etc at more than double the price of mine.

So if you're on a budget, get one of these.

As for the torque setting, GTRtwinTurbo is correct - its not good guide to go off by any means. You can buy torque limiting "sticks" which automatically limits the amount of torque output by the rattlegun to the specification off the stick but if you're particular about your torque settings just set the thing to half way when doing them up and do the rest up by hand with a torque wrench.

Pity they don't have reliable torque settings. I want to do the bolt on the flywheel pulley up, but a torque wrench and socket just makes the crank turn. No good if I can't rattle it up to the exact torque! Might as well use an impact driver and hammer and whack the BEEP out of it!

Gotta lock the crank dude :P

Yep, gotta lock the crank. Make the tool out of tube steel and a few bolts, easy as!