These are parts that I like to use in my bots. I'm not saying they are the best, but I try to find affordable and reliable parts.
See Motor Test Results for data on these.
- ZOSKAY 35kg Servo - Torque and can be overvolted to 3s
- HennkeWell Plantetary Gear Box - 84:1 - Kinda heavy, but super cheap at about $3/per box. Works well with large wheels when paired with a "nerf 130 motor"
- Valkyrie "Nerf" 130 Motors - super cheap and very powerful at around $3
- FS2A Receiver - These are tiny and cheap. They have 4 channels, which is usually enough.
- Rectified Robots Double ESC - Tiny, affordable, and pretty robust, but they do have some availabilty problems