Puns in Shakespeare's sonnet CXVI?

Question

What are the puns in this sonnet:

Let me not to the marriage of true minds

Admit impediments. Love is not love

Which alters when it alteration finds,

Or bends with the remover to remove:

O no! it is an ever-fixed mark

That looks on tempests and is never shaken;

It is the star to every wandering bark,

Whose worth's unknown, although his height be taken

Love's not Time's fool, though rosy lips and cheeks

Within his bending sickle's compass come:

Love alters not with his brief hours and weeks,

But bears it out even to the edge of doom.

If this be error and upon me proved,

I never writ, nor no man ever loved.

Answer 1

Many, if not most, of Shakespeare's sonnets, depend on puns for their full meaning.  However, this is one of the most rhetorical sonnets, and it does not rely on puns.  Another peculiarity is that the sonnet is couched as pure argument: it does not address particularly to the `Young Man' at all.  Why do you ask this question?  

I think the only actual pun in this poem is on bend-- in line four, it conveys a vague sense such as comply.  In line ten the word takes on two meanings: cheeks/[which] within his bending sickle's compass come are, really, cheeks which bend and droop with the passage of time, pointing back to the concerns of the earlier sonnets.  This fills in the meaning of the earlier bend: unlike physical processes, love is numinous and does not bend in this way.  The other meaning of Time's bending sickle is simply that the sickle is literally bent.  This whole metaphor is weirdly mixed, because `Time's bending sickle' is really the grim reaper's scythe; and the idea that it is responsible for the mundane processes of ageing is bizarre.

Another formulaic pun is that in `Time's fool,' `fool' means illigitimate child; but figuratively it only means something subject to time.  This is the same formula as when Romeo complains, `O I am Fortune's fool!'

It is possible that `proved' and `writ' in the couplet are Elizabethan legal puns as well, but I am not very sure about this, and the sonnet does not emphasise the point much.

The repeated use of `alter' is not punning.

So devoid of puns is this sonnet that some of my friends joke that by love, Shakespeare actually meant the Chinese renminbi; and by impediments, he means the Asian financial crisis of 1998.  This interpretation makes `ever-fixed mark' a pun on the German Deutschemark.