Can anyone share their favourite knots?
I suspect that you are after fancy tying-up techniques, but I think it worth mentioning the following.
For a beginner, or even when playing with someone for the first time, the lark's foot is absolutely essential. The more the tied person pulls against it, the tighter it will get, so great for getting into the struggle. However, if the tied person relaxes and gently moves their wrist it will steadily come loose and they can slip their hand out, which could be useful in an emergency or if they are not happy. It is also very quick and easy to tie, so moving the fun forward quickly if you are not just there for the knot tying.