[blasek0]

It would be nice if OOTP added calculations for and the ability to view a few more stats, such as:

For hitters:
wRC+, because OPS+ does not properly value offense

For pitchers:
Percentage stats, rather than K/9, BB/9, etc. So K%, BB%, HR%, H%, and XBH%. Per-9 stats can be inflated/deflated by a pitcher who's absurdly good/bad due to changes in the number of outs made, especially when you're measuring H/9, HR/9 and BB/9, since none of those events result in outs. Adding the percentage based version based on batters faced avoids that problem, and allows players a more accurate view at what his actual rates are.
FIP+, because ERA+ and FIP already exist, and FIP+ is better than FIP because not all parks are created equal
Actual fly ball / line drive / ground ball rates, rather than just plain GB/FB
Swinging Strike percentage
The family of "Plate discipline" stats, such as First Strike%, Z-Swing%, Z-Contact%, O-Swing%, O-Contact%, Zone%, and the aforementioned Swinging Strike%
Pitches per batter faced
OPS+/wRC+ against, because these can tell you things that ERA, FIP and FIP+ don't tell you.