I have a old school Dremel MiniMite 2-Speed 5K and 10K RPM it works great. I think the new ones have a higher RPM than mine, but the couple people that have the newer ones say they are not to bad. The Mini is cordless and mine lasts for a pretty long time (3-4+ hours) unless I am cutting a bunch.
The other option is the
300, it has a cord but it is one of the only one that has a variable speed that goes down to 5K RPM, because 10K or more is just way to fast for most projects. You will either melt the plastic if using to modify or cutting, lose a finger or at least a larger percentage of it <--come close a couple of times
If this is your first Dremel I would go cordless all the way you will use it 90% of the time, and if you need to do a lot of cutting or grinding just borrow one from someone who has a corded one.
Anyway hope that helps...also if buying extra tools DO NOT get the cheap ass 4000 Accessories for $20 from Sams or Cosco. They may seem nice until you need to do a real project then buying the real deal Dremel extras is the way to go just a much better quality on the cutting wheels and bits and such.
Punctuation ~ its late so read slow and add as needed...