From the flight deck on a recent Frontier flight, after touching down with about 3 minutes left in the most recent Super Bowl:

"Was that my landing you all were cheering for?"

A few years ago:

"Please remain seated while our pilot taxis what's left of our plane to the gate."

On a DL flight from SAN to ATL last year (from the pilot)...

'We've surveyed the children on board and 5 out of 7 would prefer us to fly the plane upside down. However donations to the pilot's retirement fund could convince us to fly it right side up',

and

'the flight could be a little bumpy today but unlike other airlines we don't charge extra for the bumps'

'twas rather amusing :)

On a recent VS flight DEL-LHR. This announcement was made in Hindi and was done very matter of factly (they do all announcements in English and Hindi):

"Please make sure to check your seat pockets for anything important and expensive you may have left behind such as cell phones, iPods, etc. Anything you leave behind will be divided evenly amongst the cabin crew. Thank you."

Heard at Baltimore/Washington area airport (I won't say which one) from an NW GA after a Delta flight was boarding with the GA using zone boarding:

"At this moment, we'll be pre-boarding our First Class passengers and Elite card members. Later on, we will be boarding by classes, not zones, this is only an airplane people, there won't be a spaceship for about another century."

Pretty decent laughter around the gate area. I looked over to the Delta gate to see if the agent there was paying attention, nope.

"...the designated smoking area for this airplane is the right wing..."

"Just to let you all know, I am not an airline pilot, but I did stay in a Holiday Inn Express last night."

Before US LAS-LAX on 2/14/09

BA flight into LHR:

Pilot: "Doors to manual and cross-check. Well done cabin crew, have the rest of the day off!"

My son thought it was the funniest thing he'd ever heard onboard.

from the same AF purser, various announcements during an intra european flight:

"the cabin crew will be able to speak english, german, italian, spanish and a few words of ...french.
"return to your seat, put your seat belt ...and stop shaking that plane"
"we just arrived in XXX, the weather is 23° degree celcius...inside the plane and 8° outisde"

On a late afternoon, very short Tucson to Phoenix flight a couple of years ago the FA had obviously made her boarding announcement more than once that day and was jazzing it up to get/keep everyone's attention.
So while doing the bit about electronics in flight she said if you really need to get out that laptop please feel free to do so in the 2 minutes of cruising prior to us starting our descent into Phoenix.
At the end of her announcement she asked if we wanted to hear a joke which went “why did the mermaid sit in the seashell; pause, because she could not fit in the B shell.
It was a very tough crowd and she did not get many laughs, mostly the men, but it made me laugh out loud after a very long day.