We are lucky enough to have access to a Universal Laser Systems 50watt laser cutter. We have found this to be quite useful. We are using this machine, to make components for the Throttle motor gearboxes
http://imgur.com/a/uJlaR that we are distributing to International rookie teams. We also just recently made a dozen large plaques from 6mm clear acrylic to thank our sponsors. Most laser cutters can cut 3mm and 6mm (or ¼ inch) mdf or plywood very quickly. Due to the relative low cost of mdf and plywood compared with Aluminium. Gussets and gearbox plates etc. can be designed and prototyped on a laser cutter before manufacture from Aluminium on a CNC mill or router.
Last season, we made a lot of spacers, especially hex ones on the laser cutter, these were mainly from Acrylic, which isn’t the best material, especially when pop riveting but it isn't possible to make hex spacers on a CNC mill or a router without a broach. An important thing to consider when selecting a machine is the software. With the right software and a bit of experimentation, you can make material profiles and presets. I have done experimentation with power and speed settings, and have been able to cut Delrin and also Polycarbonate to a usable standard ( with adequate extraction and filtration of not so friendly exhaust gases), but this necessitates constant lens cleaning due to chemical deposition and doesn't leave you with the best looking parts.
A laser cutter can be an effective and efficient way of prototyping and producing robot parts, it can also be effective for making plaques, trophies and give-aways. You really need to consider how you will use the machine, if you are going to take the approach of making many robot parts on the machine then it can be highly effective. However there is a significant initial cost associated with purchasing and setting up the machine. I would personally consider a laser cutter to be a low priority, but it really depends on how you want to build your robot. If you want to go down this path, you might be best off purchasing a cheap one from China. This is because manufacturers such as Epilog and Universal Laser Systems make good machines, but are expensive especially for a model with a large bed.