They can have most human meats, cooked or uncooked, but chicken is probably the best and is ideal if you're going to start experimenting with raw (wings are good). If you give it him cooked, make sure you remove the bones, if it's raw then you can leave the bones in as they're soft when uncooked. There are varying reports about pork - some people say cats can find it hard to digest and that it can cause worms but it's included in a lot of processed pet foods. Cooked fish is OK but avoid tinned fish which can have high levels of salt and oils in it which isn't good for them.
Mine often snatch little bits of human food when I'm preparing meals (or eating them
). Dolly will try to lick butter off toast and she begs for a bit of cheese when I make by sandwiches for work so I usually let her have a tiny amount. I figure that tiny bits of human food aren't going to do her any harm but I wouldn't give her anything substantial because she needs to know that her main food is what goes in her bowl.