Although there are new and interesting, like the shake weight , it is ideal to stick to the classics. Here are the top 5 popular equipment pieces that every gym should have. Although unassuming and seemingly simple, a stability ball is a vital equipment that should be present in every gym. There are a number of reasons why the stability ball is so popular in the gym. First, it can be used by anyone and everyone, irrespective of the level of fitness you possess.