If you are looking for a folding knife, most likely you will find an "Americanized" tanto blade shape like the one Ernie Emerson and other companies often feature.....

- Emerson Mini CQC-7B BTS.jpg (25.98 KiB) Viewed 2870 times
.....it is shaped differently than the traditional Japanese Tanto, described above by Greg. Maybe he will post a picture as well? There are also a lot of "Modified" Tanto shapes from Benchmade, CRKT, Cold Steel and others.
Ernie Emerson and others have penetrated car doors...but, I believe it was more of a test of the strength of the linerlock in combination with that profile, than just the the tanto alone as a penetrator. Though the shape is touted for it's piercing ability.
Just what I've heard.
Bill
EDITED...For clarity.