PITCHf/x doesn't have every pitch thrown, it does include 280 home runs from the 2009 regular season (through April 15).  Here are some notable pitches that were returned rather abruptly.

Fastest Pitch
Travis Hafner off Brandon League (4/12 CLE)
97.1 MPH Fastball

Slowest Pitch
Travis Snider off Kevin Slowey (4/13 MIN)
73.4 MPH Curveball

Highest Pitch
Adam LaRoche off Brian Moehler (4/13 PIT)
48.5 inches from ground

Lowest Pitch
David Wright off Walter Silva (4/13 NYN)
14.0 inches from ground

Widest Pitch
Adrian Gonzalez off Mike Pelfrey (4/13 NYN)
13.8 inches out from center

Tightest Pitch
J.J. Hardy off Edinson Volquez (4/13 MIL)
14.6 inches in from center

Wright and Gonzalez exchanged blows at the opening of Citi Field.  Oddly, all but one of these home runs were hit on the 13th.

Plenty of "balls" have been hit for home runs so far.  Here are the early leaders.

Most Home Runs Hit on Pitches Out of Zone
2 Jorge Cantu
2 Carlos Delgado
2 Adrian Gonzalez
2 J.J. Hardy
2 Aaron Hill
2 Albert Pujols
2 Grady Sizemore

Most Home Runs Allowed on Pitches Out of Zone
3 Scott Baker   
2 Jamie Moyer 
2 James Shields
2 Justin Verlander
2 Edinson Volquez

One of Aaron Hill's is one of Scott Baker's, and it resulted in the photo shown above.