Boom Chicka Boom
(source: "Campfire Activities", Girl Guides of Canada, 1993.)
(leader sings line, everyone repeats)

I said boom!
I said boom chicka-boom!
I said booma-chicka-rocka-chicka-rocka-chicka-boom!
Uh huh!
Oh yeah!
One more time...

Some Extra Verses:

Underwater: sing with fingers dribbling against your lips
Loud: as loud as you can!
Slowly: as slow and drawn out as possible
Opera: sing in an opera voice
Tongue in Cheek

Verses with Special Words:

Valley Girl:
I said, like, boom!
I said, like, boom chicka-boom!
I said, like, booma-chicka, like, rocka-chicka, like, gag me with a spoon!
Like, uh-huh!
Like, for sure!
Like, same thing... 

Thanks very much to Traci for this cool extra verse!

Janitor style:
I said a Broom-Pusha-Broom,
I said a Broom-Pusha-Broom,
I said a Broom-pusha-mopa-pusha-mopa-pusha-broom.

Thanks to Kendra Kelly for this extra verse!

Barn-yard Style:
I said a moo chicka moo
I said a moo chicka moo
I said a moo chicka bocka chicka bocka chicka moo...

Thanks very much to Diana J. for these verses!

Flower Style:
I said a bloom.
I said a bloom chica bloom.
I said a bloom chica blossom chica blossom chica bloom...

Race Car Style:
I said a vroom.
I said a vroom shifta vroom.
I said a vroom shifta grind-a shifta grind-a shifta vroom...

Astronaut Style:
I said a moon.
I said a shoot-me-to-the-moon.
I said a shoot me blast me shoot me blast me shoot-me-to-the-moon...

Mr. Rogers Style:
Can you say boom?
Can you say boom chica boom?
Can you say boom chica rocka chica rocka chica boom?
Can you say uh-huh?
Can you say oh yeah?
I knew you could!

Thanks very much to Rachel Rivera for these extra verses!

Parent's Style:
I said a boom go to your room
I said a boom go to your room
I said a boom go to your room and don't come out 'til next June.

Photographer Style:
I said a zoom chica zoom
I said a zoom chica zoom
I said a zoom chica click-click chica zoom

Thanks to Sue Markle for these verses:

Grandpa style: sing while pulling gums over teeth
Baby style: sing in a baby type voice
K-mart Style: hold nose and sing
Frankenstein style: hold arms straight out, and sing in a deep voice