You should first decide whether you want an analog delay, or a digital delay. They are very different. Analog has a certain "tone" to the repeats that some digital, delay's try to emulate, some fairly well. Digital delays offer much longer delay times, as well as a host of different features, depending on the particular unit you choose. For analog, the Carbon Copy is good, but basic, the EHX Memory Toy/Boy series have more options, and digital, the TC Electronics Flashback is good, as is the Boss DD-20, or DD-6, etc. You can spend ALOT more for some like Pigtronix or Strymon, but you may not need what they offer.