Depending on what you'd want it for, you have several choices:
Bold... slightly bigger, but not by much and it doesn't feel bad in hands. 3g is a plus for simultaneous voice and data as well as faster data downloads/uploads
Curve 8900... Faster processor than the curve, 3.2mp camera, and has a better resolution screen than the Curve/Bold/Pearl. This also has more application memory and if you like to d/l a lot, this is a plus.
Pearl... great for the size and you don't even know it's there. Easy for one hand typing. I still type faster on the Pearl than any other full QWERTY Blackberry.
Curve... I wouldn't even think about this as it older brother, the Curve 8900 kicks it's arse in every category.
Also, if they aren't going to use a data plan, you can save money by not getting a 3G phone. They are more expensive (because they are newer) unless you get the 8900 (Brand new Curve with no 3G). The Pearl and the Curve 83XX are the cheapest options.
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