1) Barbell wrist curls

Great forearm flexor exercise. It does a good job of isolating the target-muscle.
The subject sits on a horizontal bench with a leg down both sides of it. Laying the forearms onto the bench he/she lets his/her wrist and hands hand off the edge of it, and in the same time straddles his/her elbows with the knees to further stabiles them. Taking a barbell into the hands (close underhand grip) he/she slowly lowers it only moving his/her hands (forearms completely stationary) when at the bottom of the motion he/she lets the barbell roll a bit out of his/her palm onto his/her fingers then lifts it back up as high as possible without taking the forearms off the bench.
Extra considerations: forearms are rather difficult to stimulate. One needs to do more reps than usual to really make them work