Question: Is there a single word that sums up "taking one for the team"?

In this instance specifically doing work alone that would normally be done by a small group, so that others can rest.

* Loyalty
* Dedication
* Integrity
* Sacrifice

all seem to (me to) be sub-par.

Answer: 
There are a few that would qualify: selflessness, self-denial, self-sacrifice, self-abnegation, etc. They all mean something like this [from NOAD]:

> 
> **selflessness**  
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> *adjective*  
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>  concerned more with the needs and wishes of others than with one's own; unselfish: *an act of selfless devotion*.
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> 
> 1. take one for the team  
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>  The act of someone willingly making a sacrifice for the benefit of others.
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> Example: There wasn't enough room in the car, so Jerry decided to take one for the team and stayed behind while the rest of us went to the big concert. 
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**wingman, team player, sacrificial lamb, good sport, buddy**

> 
> **self-abnegation** *n*
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> 
> the denial of one's own interests in favour of the interests of others
>  self-abnegating adj
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> 
> **self-renunciation** *n*
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> 
> the renunciation of one's own rights, claims, interest, etc., esp in favour of those of others
>  self-renunciatory adj
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>