The European Central Bank (ECB) surprised many in the markets on Thursday by cutting its main interest rates to a record low of 0.25 percent in an attempt to help kickstart the euro zone economy.
But what's left in President Mario Draghi's arsenal if the bank needs to unleash further accommodative steps after this week's cut?
"We are doubtful that the ECB can still offer many of these big-bang days in the future," Carsten Brzeski, a senior economist at ING said in a research note on Thursday.
The policy move has increased the ECB's reputation as the euro zone's "pro-active firefighter", he said, but the cut will hit the ECB's predictability and make future forward guidance and market expectation management more complicated, he added.
(Read More: ECB rate cut joltsmarkets, but is it the fix?)
"On-going deleveraging in both the private and the public sector should exert further deflationary pressure which will be hard to tackle by monetary policy. Let's not forget that there have been more of these pulling-out-all-the-stops days at the ECB over the last years with cheerful reactions on financial markets but limited impact on the real economy."
Richard Kelly, senior global strategist at TD Securities, told CNBC that if the downside risks to growth are bad enough, then the ECB knows it will have to respond and Fed-style bond-buying programs -- know as quantitative easing (QE) -- could be the only option.
"They really don't have anything left, this was their one shot to weaken off the euro. After this it really is negative rates or QE," he said.
"(QE) really becomes the only option and you really would expect very loud volatility going around that."
As well as cutting its main interest rate by a quarter point, the ECB trimmed its emergency lending facility by 0.25 percentage points to 0.75 percent. It kept its deposit rate at zero. While speculation increased about a rate cut after a very low October inflation reading, many strategists had not expected the ECB to make a move until December.
Also Thursday, the ECB decided to extend a fixed-rate, full allotment regime until mid-2015. Analysts see this extra 20 months' worth of liquidity as giving euro zone banks a safety net ahead of the ECB's asset quality review and stress tests next year - but could also indirectly provide a rough estimate of how long a period the ECB's forward guidance might cover.
(Read more: ECB rate cut: Analysis and reaction)
The euro's sudden fall and a rally for stocks after the decision is a sure sign of how unexpected the central bank's move was. When asked about further measures Draghi said that the ECB was "technically ready" for a negative deposit rate in inflation continued to founder. This would effectively charge banks if they store deposits at the central bank, thus urging more flows into the real economy.
"We want to have some instruments in our artillery and this is one," Draghi said, adding that LTROs (long-term refinancing operations) were another - a process by which the ECB provides liquidity to euro zone banks.
"We did not discuss this in any depth today, but there are a whole range of instruments that we can activate, if needed," Draghi said.
The president even stated that the main refinancing rate - the interest rate that banks have to pay when borrowing money from the ECB - is yet to reach zero despite Thursday's cut and could be pushed lower. "We have a whole range of instruments that we can still activate before reaching the lower bounds," Draghi reiterated.
Jens Nordvig, global head of FX strategy at Nomura told CNBC that the rate cut was a good "signaling mechanism", indicating that the bank was still ready to act.
"Saving bullets is the wrong strategy for a central bank, I think you need to be aggressive but I think it's also important to keep in mind that you know exactly how many bullets they have because we don't know exactly how the toolkit looks," he said.
(Read More: BoE leaves rates, asset purchase target unchanged)
"So I think what Draghi did yesterday he's trying to hint that, yes, maybe they have more bullets than we thought they had."
Frederik Ducrozet, a senior euro zone economist at Credit Agricole said that another bout of long-term low-interest loans – known as long-term refinancing operations -- looks more likely to be used than other tools, but it would depend on data and liquidity conditions in the coming months.
"The ECB still views inflation expectations as firmly anchored. But, if they start to drift lower on some measures, it would be a clear trigger for further easing measures," he said in a client note on Thursday evening.
By CNBC.com's Matt Clinch. Follow him on Twitter