Pull-Buoys: These can be broken into two main types, solid and two piece. The solid type are not adjustable, but they do not move or shift as much as a two piece buoy. Pull-buoys with two separate floats, joined by a rope or band can be adjusted to fit the individual swimmers leg size.
An additional piece of pulling equipment is an ankle band. Wrap a large rubber band, small inner tube, or circular float about the ankles to stop all kicking action. This can bring out some body position and pulling flaws that might not otherwise be noticed. It also adds to the workload.
Hand Paddles: Adding paddles to either swimming or pulling can increase speed and feel, making some stroke flaws more obvious. Using paddles also adds an extra load to the workout, which can result in improved conditioning - or an injury. Swimmers must complete each stroke with good technique and listen to their body. If something hurts, stop!
Generally, if the paddle is rectangular there is an increase in the ability to put pressure on the water in the catch - but this also means more stress. Paddles that are curved or tapered tend to have less surface area, resulting in less stress - but also less pressure or power. A few designs include holes drilled through the paddle to keep some water flowing through it. This can both decrease stress and maintain the feeling of flow throughout the stroke. Some companies also make a webbed glove; this design is more suited to aquatic exercise as opposed to lap swimming. Paddles come in a wide variety of styles, each with its own claim as to why it is the best.
Kickboards: Big, little, hard, flexible, even some that look like spaceships, kickboards should be comfortable to hold but not so buoyant that they lift you too far out of the water. Many swimmers find that using flippers while kicking helps them to both build stronger legs and increase ankle flexibility. Kicking with a board is probably most productive when done with the face out of the water and the arms on top, gripping more towards the front. Using a board alters your body position, so it is a good idea to kick without a board sometimes, too.
Whatever you choose, attempt to try it out before you buy it. Individual comfort varies from type to type, and the one that you think looks the best may make you feel the worst.