I have a gym in my garage, consisting of a electric treadmill, multi-gym, rowing machine, skier thing and the stuff I use the most (Which isn't often admittedly), my cast iron dumb-bells.
All those pulleys and cables, but two lumps of solid metal do the job the best.
oh Karl's got those blue dumb-bells except his are red and black!! and thankfully there are round so I can roll them across the floor when it comes to hoovering his room..certainly would not attempt to pick them up