I absolutely hate people that mask their favours in bullshit conversations that at the end of it mean nothing when you whack out the "oh, by the way can you", "oh yeah that reminds me", "when you get a chance"...
The worst are when they ALWAYS invite you over when you KNOW there's going to be something they want you to do.
Another all time favourite is using their children as a reason to come over then they surprise you with something to do for them.
Of course all of this is free and if you even think about charging them you'll be sent straight to hell.