The nickname "Ronson", after the cigarette lighter, is often applied to Sherman’s "because they light the first time". The trouble is the Ronson company didn't use that slogan until several years after the Second World war. The closest anyone has found is this advert from the 1950's.
There was a Sherman Ronson though, it was a flamethrower armed tank, but like a lot of Sherman based flamethrowers it lacked performance. It is a popular myth that Sherman flamethrowers never took part in the fighting in Europe, but that's not strictly true. But unlike the nickname Ronson, they performed rather poorly.

In mid 1943 the three main western allies held a conference about flamethrowers. The result showed that the US were trailing behind the other two nations, this spurred the US army to accelerate its attempts at flamethrowing vehicles. Earlier in the year the US had seen a demonstration of the Churchill Crocodile. Suitably impressed the US delegation was informed that the Crocodile kits should be able to be fitted to M4 Shermans. This would mean the US forces wouldn't have had to take on a foreign vehicle. Towards the end of 1943 the US army started sounding out the British on the idea of Sherman Crocodiles, requesting that about 100 Shermans should be converted. The British then provided a wooden mock up for the US officers to view, whom in turn agreed that the design should be prototyped. At the start of 1944, after seeing a demonstration the US placed an order for 115 conversions, although in reality only four would be completed.
I believe this is the mock up. Note the early mud guards and odd looking flame gun compared to later photographs.
For the modellers out there, it should be noted that the British were to provide common parts of the Crocodile design, so its likely the components would be painted in S.C.C. 15 Olive Drab, which as you know weathers differently to the US colour. Of course the US may have repainted the British parts with standard US colours, so pick whichever you think looks best.
Early US Flame thrower tank
Alongside this the US domestic programs had continued. The design that was selected as an auxiliary flamethrower, designed to replace the .30 calibre bow machine gun. Two packs consisting of a 25 gallon tank and pressure cylinder were fitted inside the tank at the hull gunners position. The entire fit-out weighed only 997 pounds. There were no outward visual changes, so even a modified Sherman with the E4-5 kits would be visually indistinguishable from a normal Sherman.
E5R1 flame gun
One conversion kit was requested in April 1944, and was shipped in June. In a demonstration in the UK on the 23rd of June, and a repeat performance in Normandy in August it performed rather badly and failed to light. After re-working of the design several kits were airlifted into Europe arriving in September, when it was issued to front line units.

The crews who received the kits were less than thrilled at the idea of adding more fuel to a tank that was already regarded as a fire trap. Equally all the extra tanks and fuel canisters made evacuation from the tank harder, with the bow gunners hatch being partially blocked by one of the pressure cylinders. The emergency alternative escape hatch was blocked by a fuel tank.
Wherever possible the kits were installed in Sherman Jumbo's. Things carried on going badly for the E4-5. The 741st Tank battalion had two E4-5 equipped tanks attached to it, however one broke down immediately leaving one to go into action on the 18th of September.

Its target was a German held bunker. The stated range of 70 yards quickly turned out to be false. The Sherman had to advance to within 25 yards before the flame could hit the bunker. Even then it was utterly ineffective and the Germans remaining inside their bunker were not harmed. The after action report suggested that for some unknown reason the flamethrower wasn't firing at the correct pressure. This problem was to plague the E4-5 system, along with a tendency to fail to ignite. This happened to the 743rd tank battalion near the Roer river, when a E4-5 flamed a group of Germans occupying a roadside ditch. The Germans were soaked by a wet burst of flame fuel. In the same operation a E4-5 did show what it could do, when it was used to flush out German defenders occupying a house on a hill. The slope of the hill meant that the Sherman’s could only shoot at the upper floors of the house. But the flamethrower could place effective fire on the lower floors by lobbing the fuel over the crest of the hill. It forced the Germans to evacuate the position.
To further compound the problems suffered by the E4-5, the system had been introduced without properly trained personnel. This was almost certainly the cause of a massive explosion that happened when a pressurized cylinder of oxygen, rather than nitrogen was used in the system. The other issue of course was the terrible range the system gave, it meant the Sherman had to enter effective range of the German Panzerfausts before it could stand a hope of hitting its target, assuming the system worked.
But what of the Sherman Crocodiles? In November 1944 they were issued to a mine exploder platoon of 739th Tank Battalion. During the remaining few months they only used their flamethrowers once, at the town of Jülich during Operation Grenade on the 24th of February.
The city was seized, however the Citadel remained in German hands. It was heavily fortified and ancient fortifications still work after a fashion, even today. Any infantry assault would have caused massive casualties. For example the first obstacle was an 85 foot wide moat. The mine exploder platoon was brought up to reduce the fortification. However two of the tanks broke down or became immobilised in the rubble of the city. The attack was strangely similar to the Churchill Crocodiles assaulting Brest. The two Shermans halted on the edge of the moat and incinerated the positions facing them. The Germans were forced to retreat from the area. The Two Shermans then pummelled the main gate with their 75mm's, blasting it open. Then the tanks clanked slowly across the bridge, with their trails of fuel bouncing along behind them. Once inside they set about burning everything, the bright tongues of flame spearing through the billowing smoke.
When the US infantry entered and seized the remains of the position they spotted four Germans fleeing over a hill outside the city, those Germans had used secret escape tunnels to get away from the savage Crocodiles. The Castle carried on burning for two days.