The answer here is "how long is a piece of string?"
How much do you wish to spend?
What environment is the beast going to be used in?
What country(ies) will it be used in?
Will its own mapping be sufficient or will you need to be able to download/link to external sources of mapping?
These and many other questions need(/) to be answered - isn't looking for a new toy fun (or is that a boy's thing - I love it).
I carry a simple Magellan 315 which has survived pretty well up to now although it is showing its age a bit. Very useful for sticking under the cab driver's nose when he claims to have dropped me off at the correct grid
It's for my chap. Why would girls want one when we are blessed with such incredible innate sense of direction?
I am not sure I can answer all of heavy's good questions though - but money is no object and he will potentially need to use it anywhere in the world. I will work on the basis that he will not need to download. So if someone were buying you one as a surprise, what would you like to get?
Sinner..... don't worry - I am sure you make up for it in other ways...