I loved all the oddities and funny things in Fallout 3. The factory with the teddy bears in naughty poses doing... naughty things was pretty clever and funny.
Easter Eggs were like everywhere in Fallout 3. I missed them a bit in Fallout New Vegas, of course there were much bigger pop culture references but few little funny secrets / oddities.
How about some "Ladidadidah. Explorin' a random cave. Ouch! Something is attacking, let's turn around and see what......HOLY DEAR GOD IT'S A GIANT FRIGGEN SLAUGHTERFISH RUNAWAYRUNAWAYRUNAWAYRUNAWAY"
I remember a thread awhile ago talking about Easter eggs. One of them was a closed oblivion gate somewhere around the border and the other one was a bunch of cliff racers frozen in a block of ice .
(well the original idea was just one cliff racer but I made a suggestion to put twenty frozen cliff racers to make it more believable)