The ones that stood out were:

Microsoft's project "Natal,"

Nintendo's Vitality sensor,

And Sony's motion controller.

Ofcourse you can post your personal favorite "joke of E3," or even just an awkward,funny moment like some of you have already posted.

vitality sensor

I think project natal is good but it was funny when he tried to show the bottem of the avatars foot.

on Microsoft.

im going for Natal girl , she was like a retarded monkey, and "BAM THERE IT IS!" , and that guild girl. and also Don clapping for himself

on nintendo.
4 Mario games? you're serious? , Iwata's speech was waaaaaaaaaaaaaaaaaaaay too long , not much games (other than mario) were something i didnt know about.

on Sony.
the motion controllers looked like a dildo, PSP Go! is "Worst Kept Secret of E3" , Jack Trenton is funny made alot of joking around.

"Oh look a few sold right there" - Jack Tretton talking about the lilac psp.

I think the vitality sensor... That thing is just pointless to the mass audience of gamers!

I laughed at the Sony motion controller. Not because its a bad idea, but because their presentation of it wound up being so similar to both Nintendo's presentation of their tech (like how the Sony guy was showing Tennis and especially archery), and then with Microsoft's presentation (with the painting)

Certainly not intentional on Sony's part, just an unfortunate fact of them going last, but it made them look like a bunch of copycats

nintendo

PSP go! being the worst kept secret of E3, that was funny

I'm sorry but that PS3 controller look a lot like a dildo. and I'm sure it can vibrate too.