In my experience, my favourites have included:
Tantus O2 Adam, a nicely sized, pleasantly curved dildo with a softer outer layer of silicone reinforced by a more firm core.
Fun Factory Tiger, a long and rippled shaft with a bit of a curve of its own; very firm and definitely good if you enjoy bumpy texture, but do be warned that it's more than just noticeable.
Tantus Ripple Large, while more of a probe than a dildo, provides the thrusting aspect of a dildo with the graduated 'popping' of anal beads.
There are plenty more, of course. Variety is rarely a problem... Choosing is! Good luck.