Some bologna and kielbasa has garlic in it. You don't want to feed garlic to a cat. And I don't suppose the other ways the meat is "smoked" and flavored are especially good for them, either. This is true for adult cats and double for kittens. If you want to give them something that's free of onion and garlic, then I suppose a little bit as a treat wouldn't hurt. But I'd suggest you stick with cat treats.
Yeah, I would be careful especially with processed meats, as you don't always know whats gone into them.
A little bit of ham or chicken breast would be ok, but just be careful as you could end up with a kitten with nasty diarrhea.
A little bit of tuna (in brine or freshwater) would be ok.
If you really wanted to give a kitten a treat - Give them some BBQ chicken (No skin of course) - They LOVE it, and this is what I was recommended to feed my kitten when he was young (from the vet)
As the others said, don't feed them any smoked cold cuts. Plain cooked chicken or turkey is fine occasionally, they should still get a proper cat food for most of their meals. Tuna is only OK for a very rare treat, frequent feeding of tuna can cause major vitamin deficiency. Although tuna flavored cat food is OK.