At one point Sunday, oil futures were trading lower by as much as 30% after the Organization of Petroleum Exporting Countries failed to reach an agreement with some previously cooperating countries — namely Russia — to cut output in a bid to prop up already sagging prices.

Amid speculation that Russian President Vladimir Putin is willing to participate in a price war, Saudi Arabia beat him to the punch as the kingdom, OPEC's largest producer, said it will slash prices on oil exported to China and actually boost production.

With Sunday's goings on, it's widely expected that when U.S. markets open Monday, oil will be trading around $30 per barrel, which could spark significant rallies in some or all of the following bearish exchange traded funds.

MicroSectors U.S. Big Oil Index -3X Inverse Leveraged ETN (NRGD)

NGRD hails from the same fund family as some well-known, leveraged and inverse FANG exchange traded notes (ETNs) and looks to deliver triple the daily inverse performance of the Solactive MicroSectors U.S. Big Oil Index. That benchmark is a collection of 10 equally-weighted oil names, including Exxon and Chevron.

NRGD gained 17.68% Friday, meaning it's up a staggering 89.59% over the past month.

VelocityShares 3x Inverse Crude Oil ETN (DWT)

The VelocityShares 3x Inverse Crude Oil ETN (NYSE:DWT) tries to deliver triple the daily inverse returns of the S&P GSCI Crude Oil Index, meaning it's sure to be in focus on Monday.

Home to nearly $153 million in assets under management, DWT is coming off a Friday in which it surged 27% on volume that was more than double the daily average. That should put an exclamation point on a year-to-date gain of 171%, but there could be more coming for DWT.

With oil poised to crater Monday and Goldman Sachs warning $20 a barrel is possible, DWT could have some more near-term upside ahead. 

Direxion Daily S&P Oil & Gas Exp. & Prod. Bear 3X Shares (DRIP)

Perhaps saving the best for last, the Direxion Daily S&P Oil & Gas Exp. & Prod. Bear 3X Shares (NYSE:DRIP) will almost certainly notch an epic Monday move in one direction or the other. With oil flirting with the $30s and in the event Goldman's $20 forecast proves accurate, these are dire straits for exploration and production firms.

That's applicable even to the sturdier names in this group, because those companies have higher break-even prices than what oil is sporting today.

DRIP, which looks to deliver triple the daily inverse returns of the S&P Oil & Gas Exploration & Production Select Industry Index, gained 29% last Friday and is up nearly fivefold year-to-date.