I am a pretty Booterfly
He's a Boofoon
I'm the great Booletta
Pikaboo, I see you
Boohoo, that's so sad
I am King Booser
I am Turboo, and off I go (Okay this one was from Luigi's Mansion but I remember a few lines from the game so it doesn't count)
He was so Boonswoggled (I know what Boonswoggle means and that explains why he's the fastest Boo in the game XD.)
My name is Booris
I'm a miniature Boodle

Alright I ran out of them! Boo!

MarcusMasteredMilk made the most puns in the comments.

Anyways, top 5 favorites from the comments
5. I'd make a pun but it would be Boo-ring, MarcusMasteredMilk
4. I look Bootiful, Aureialshipper
3. One time Mario and Luigi went Boowling ,MarcusMasteredMilk
2. I saw Kamek picking on a Toad. What a Boo-ly, Marcus
1. When Bowser is in a haunted mansion he becomes King Boo-pa