Question: The recently detected gravitational wave at LIGO were extremely small - requiring a $1 billion interferometer to even detect its presence as it passes Earth.

The gravitational constant G is small: ~$10^{-40}$ times that of the electromagnetic coupling for protons. But then, there are lots of really massive, energetic things in the universe - much more massive than the black hole merger that was observed - so my question is: 

**Are there any potential sources of *significantly* greater gravitational waves that could be detected without sensitive instruments?**

As one commenter pointed out, this is a little like asking [what a lethal dose of neutrinos would be](https://what-if.xkcd.com/73/). In Randall Munroe's words: *At what point do these two unimaginable things cancel out to produce an effect on a human scale?*

Answer: 
[Here are](http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html) the four fundamental forces:

[![funfor](https://i.stack.imgur.com/Whtsn.png)](https://i.stack.imgur.com/Whtsn.png)

What is important is the column that shows "strength" and is connected with the word "large" in the title of your question.

> 
> are there sources of significantly greater gravitational waves that could be detected without sensitive instruments, or even be disruptive to daily life?
> 
> 
> 

The enormous difference in the order of magnitude of the interactive strength should convince anybody that by the time gravitational waves from a cosmic event would be destructive, destruction would be orders of magnitude larger by the electromagnetic(fire) and strong(nuclear)and the gravitational would be unnoticed.

Fortunately our planetary system is far away from possible cosmic 
generators of gravitational waves .

So stronger waves might be detected in the future but they would still need the specially designed instruments.
Are you simply asking whether we should worry that there is an unseen menace about to unleash a "gravitational wave tsunami" upon the Earth? You shouldn't be.

Let's take the empirical evidence. The only source to have been detected is a large black hole merger. The event rate in the universe is only constrained by this and some theory to be at most about 100 per cubic Gigaparsec per year. The strain due to the event peaked at about 1 part in $10^{20}$.

To produce something "visible" (or maybe tangible?), let's say this needs to be bumped up to 1 part in a thousand (and remember this whole event only lasts for a fraction of a second). The strain decreases reciprocally with distance from the source, so the volume from within which the source could be detected decreases by the strain amplitude cubed.

So, if the current detection rate is 1 per month at a strain of $10^{-20}$, then it will be 1 every $10^{51}$ months for strains of $10^{-3}$, assuming that the sources are uniformly distributed in space and time. Scaling from the distance of the detected GW source, I note that **the source would need to be well within our solar system**. Gravitational waves would be the least of our problems should a pair of 30 solar mass black holes blunder into the solar system!

Of course you might argue that there could be other types of less extreme objects (in our solar system) that might be more common. Had there been any reasonable chance of detecting GWs from nearby sources at much higher strains (and recall that LIGO did operate at lower sensitivity for many years), then a lot of money could have been saved! Alternatively you could argue that there are rarer events involving more massive objects that produce GWs at lower frequencies than LIGO's sensitivty range. This is entirely possible and indeed likely - merging supermassive black holes could produce strains that are several orders of magnitude higher ($\sim 10^{-16}$ for a pair of $10^{8}M\_{\odot}$ black holes at 1 Gpc distance - [Ravi et al. 2013](http://arxiv.org/pdf/1406.5297v2.pdf)) at $\mu$Hz. Nevertheless, such an event would still need to be in the solar system (at 20 au) to produce strains of $10^{-3}$.