One with a voice recorder to take notes on (pinch songs with)
a silicon one with the biggest memory you can afford (not a disk drive)
One that you can use as a mass storage device on a PC

all of the above are well served by manufacturers.

One with an FM radio might be useful. If it has a clock you can time yer three minute egg - well maybe that is over-egging it a bit.

small but with decent display (if you are in the shrinking arms part of life).