The last laugh.

Three Irishmen. 

One evening three middle-aged Irishmen go drinking in a country pub. They have a lot to drink and, as is often the case, they become sentimental and start discussing the meaning of life and death.
They become so sentimental in fact, that, when the pub closes and they start walking home, they decide to stop off in the local churchyard in order to look at the tombstones.
One fellow finds a tombstone and calls over to his friends: "Look at this guy", he exclaims, "he lived to the age of 86, isn't that grand? Wouldn't you both love to live to 86? God bless him!"
"What was his name?" ask his friends.
"Let's see....er, Patrick O'Reilly"
"That's nothing", shouts another member of the trio, "this guy lived till he was 97. Wouldn't you both love to live to 97? God bless him!
"And what was his name?" ask the other two.
"Let's me see...er Seanus O'Connor", their friend replies.
Then the third member of the group starts jumping up and down in his excitement: "But that's nothing" he shouts, "this guy lived till he was 146. Can you imagine it, 146?
"Oh, come on!" answer the other two, "that's impossible! Nobody lives to 146!"
"Well, this guy did," answers their friend, defiantly.
"What was his name?" ask the others.
"Let me have a look now. Here it is: er... "Miles to Dublin".

(Source: SPEAK UP, 246)

The punch line is the last few words of a joke that make it funny.