Do all Marines, especially those in combat/infantry jobs, still get issued Ka-Bars (fighting knife), and can they keep them?

No one gets issued a knife in general. The bayonet is issued out of the arms room and its controlled like any other weapon. It's a part of the rifle and it's issued with the rifle. No...you don't get to keep it. It's military property.

When I graduated from the Special Forces Qualification Course, I was issued/awarded the Yarbrough Knife. The baddest knife in my arsenal. Yes, you get to keep it.

In 1st LAR you get issued your Bayonet when you get to the unit, granted, we used it more as a decoration on our flak. If you wish to keep one you need to purchase one yourself. http://www.grunt.com is a great site to find one, but I wouldn't buy one until you graduate bootcamp