Pulsing like a heart beat pulse that changes in frequency depending on speed, or a quick buzzing pulse?
a quick buzzy pulse would be ABS related sometimes when ABS sensor rings have a crack in them it can cause a vibrating pedal just before you come too a stop, the ABS module thinks it is wheel slip so the ABS moduel kicks in and quickly pulses the system creating a vibrating pedal sensation, a good way too test if this is the case is get a ABS compatible scanner and watch the wheel speed of each individual sensor.
have you recently done any extreemly hard braking or done a lot of hard braking then driven through a mud puddle or something?
a pulsing pedal similar too frequencies of a heart beat, that changes in frequency depending on speed, faster the vehicle goes the quicker the pulse and quite frequently more noticeable the pulse, and slower the vehicle goes the slower the pulse is quite frequently caused buy Thickness variation which can be caused buy extremely hard braking warping the drums or rotors, or run out… where the drum or rotor wobbles beacuse it hasn’t been put on right or warped… if you feel pulses in the steering wheel as well as the brake pedal it is quite possible that the rotors in the front are out of round, a good way too test this is too when you have lots of room, let your hands away from the steering wheel and press the brakes with your hands at the ready in case of any pull when breaking or in case you need too steer the vehicle quickly. if the steering wheel shakes and shimmies its probably the front brakes causing the pulsing, if not its probably the rear brakes.
and as others have said, its a good idea too get the vehicle scanned for codes for ABS