Should I train with a weighted weapon or wrist weights to get faster?
No. Adding weight to your weapon or strapping weights to your wrist is a poor way to get faster at fencing, and most coaches advise against it. Your blade actions are small, precise movements tuned to a weapon whose weight the competition rules already cap: a foil or a sabre must weigh under 500 g ready for use, and an épée under 770 g. Train with something heavier and you are practicing a slightly different movement from the one you will use on the strip.
The problem is transfer. Strength built with a heavy implement does not automatically turn into speed with a light one, and the movement you groove under load tends to be bigger and slower. Baseball offers a useful comparison: studies of weighted bats found that warming up with a heavier bat did not make the normal swing faster, and the best results came from implements close to game weight. Fencers who go from a heavy training weapon back to a light one often see the same thing, with sabre cuts that swing too wide and point actions that overshoot until they readjust.
There is an injury risk as well. The forearm muscles that control your wrist are the ones involved in tennis elbow, which orthopedic specialists link to repeating the same motions again and again until the overworked tendon develops tiny tears. Fast, repeated blade actions with extra weight on the end of a long lever load those tendons harder, along with the elbow and shoulder. If you already have pain on the outside of the elbow or in the wrist, rest it and see a doctor or physical therapist instead of training through it.
If you want a stronger wrist and forearm, train them separately with slow, controlled resistance work about twice a week: light wrist curls and reverse curls, dead hangs from a bar, push-ups and planks, adding load gradually. Then get your speed from fencing itself. Speed on the strip comes mostly from timing, a clean start with no wind-up, and a relaxed arm, so drill small actions at full speed with your normal weapon, such as hitting a target pad on a partner's signal. Your coach can tell you which part of your speed is actually missing.