I really like the dies with rounded edges and odd shapes. Things that are slightly more challenging to cut by hand.
The large drunkards path is very good-it has a gently rounded edge and a notch on both pieces for easy matching. Triangles are nice because the corners are already cut off.
The 2 I want to get are the Home and Alex Anderson's die set-basket and star.
My suggestion is to look at the types of quilts you enjoy making, are there any shapes that are consistant in all of them?