Mega- Piranha

The group the mega- piranha's belong to is #23.

Deliver Us From Evil

"This is someone we've known for 23 years."

There are a few more, but it is a touchy subject so I won't include them.

The Butcher

There are several 23's in timestamps throughout.

Daybreakers

Ethan Hawke's brother's jacket says 23 on the sleeve. I don't remember his name.

Broken Flowers

During the opening credits, one of the post office machines is tagged A-23.

Amityville Horror (2005)

George Lutz: [to Kathy] How did you get so fucking stupid?

Ronnie is 23 when he kills his family. This movie is only good for the quote seen above.

Freddy's Dead

The school therapist has only 23 minutes with the students.