The key to a good team name depends largely on what sort of team it is. It should be unique and easy to remember, and it should ideally reference the field in which the team participates.
Your team name will be what people notice first about the team, so it is important to give it thorough consideration. Branding is very important, not only in gaining support from outsiders, but also because if members are proud of their team name, this can boost morale and group cohesion.
Because the team name will represent the team, it should be poignant. You ideally want a name that is catchy, tells you what the team does, and perhaps even states the region in which your team is located. Good examples of this are sports team names. If you're a sports team, you probably want a name that represents speed, agility, power, ferocity or other such characteristics. Good examples of this are the Portland Trailblazers, the Miami Heat and the Denver Broncos.
Teams in lower-intensity settings may wish to choose milder names, but the name should still effectively represent the group. A group in a business setting might choose a name like Team Streamline or Pension Pioneers to indicate its purpose. A research group in an astronomy class might choose a name like Project Pluto or The Venus Coalition for the same reason. A team name can be silly or obvious, and you may want it to be, because names like that are easy to remember.