Kabar Becker BK-17
The BK-17 is designed after the pilot bolt knife, it has a clip point blade with a blade length of about 4 inches. The major upgrade of the pilot bolt knife is the BK-17 is full tang, versus a stick tang. This allows the added security of a heavier duty knife.
ESEE 4
The ESEE 4 is a great knife in its own right, it too has a 4 inch blade. The ESEE 4 is full tang as well and is a well respected survival knife. This was actually the first survival style knife I bought.
Kabar Fighting Knife
This is the trademark knife you see soldiers with in the movies, they have a clip point, usually longer than 4 inch blade and they are not full tang. The older Kabar fighting knives are pretty solid but I've see a decent amount of the newer production ones break.
The Verdict
If you are going to functionality I would go with the BK-17 or ESEE 4, if you are going for that classic military look then the Kabar Fighting Knife might be the way to go (just realize its limitations).