wrist curls, pinch lifting, sledgehammer levers. thick bar deadlifts. have a look at some captain of crush grippers they help a little and are good fun, or you can look at david hornes vulcan handgripper which is adjustable awesome build quality and he also does a really really good wrist developer called the orbigrip 1 minute rotating that and you can feel an awesome pump in your forearms and biceps.
Forearms are my best muscle group. When I was at school and a bit older (basically before I went to a gym) I would only ever work out with dumbells and do press ups. Gym equipment probably isolates the larger muscle groups and stops your grip strengthening as it should
I don't feel it on my forearms when I do deads. I must be doing it wrong. Anyway, outside of wrist curls hitting the bags for long periods and bicep curls help.
HEAVY deadlifts, there is no way you cant feel it in your wrist/forearm, it feels like its gonna rip off or explode.
I haven't done proper heavy lifts for a while now. Maybe a year. Just small stuff since then. I'll stack up the weights nuts like tomorrow and see what's what.
One I forgot to add earlier, and it is THE best way to develop strength in your forearms and wrists that I have ever come across is to take up riding enduro bikes - nothing comes close.