I'll agree with Jamesaritchie that I don't think it's necessarily a problem to show the ending. I think it depends on the query, and the story, regarding whether it would be persuasive to include the ending in the query. For some queries it might be very effective, for others not so much.
I'll also agree with him that I worry query critique forums sometimes result in draining bits of voice and uniqueness from a query due to group think, or even conflicting advice or advice from less than sage sources.

That's why the author needs to educate him/herself on queries and develop the ability to decide which comments to take into consideration in revisions and which to ignore.
I'll also agree that showing you can craft a well written query should be about showing a glimpse that you can craft a well-written story - to that end the query should use langauge effectively, build story tension and, whenever possible, show the voice of the book.
However, I will disgaree with him that being original is the end all be all.
Yes, the most effective queries probably stand out for some effective way - maybe a unique form, or, more likley, an effective taste of voice coupled with an effective pitch of an interesting plot.
My point is - yes, go for showing you can write, you can show more than tell, that your manuscript is well-written and has voice...but don't try to reinvent the wheel or doing something gimmicky or too weird in a quest to be original.
The most effective queries often use a proscribed format, but where they shine is through voice and that can-not-be-easily-described unique feel of the plot or language. Sometimes a single sentence is what sparks an agent's interest.
Too many "look at me! I'm original" queries crash and burn because they are just too out there, and the agents don't know the author is trying to be original - they just think the author is either a complete amateur or doesn't understand the process. And sometimes what looks "original" to the author is actually someting gimmicky that many before have tried (and failed at) so it actually ahs the opposite effect.
So, by all means, try for voice and a query that is uniquely yours. But don't tie yourself up in knots trying to be "original" at the expense of clarity. Use the examples out there as a guide in structure, but make it your own.
And, to be honest, I've come around to the school of thought that striving for perfection often drains the unique details and voice too much. Try for a clear, succinct query that effectively shows your book's primary conflict and gives a good taste of the voice of the book.
~suki