One thing I really like in Pokemon is how, for the most part at least, the several turtle-based families are different Types. We've got pure Water with Squirtle's line, pure Fire with Torkoal, Grass/Ground for Turtwig's line, and a return to Water but with a Rock subtype for Tirtouga's line.

Let's see what other turtles. tortoises, and terrapins we can make into Pokemon, using the other Types and Type combos.

My first idea is a Dragon Turtle Pokemon, similar to the ones from D&D. Dragon-type (subtype optional) that's very slow but immensely strong. Average HP and Special Defense along with very low Speed, but with high Attack and Defense and medium-high Special Attack. Learns a lot of defensive moves like Amnesia and Iron Defense and Curse, and powerful attacks like Outrage and Crunch and Earthquake and Scald. Looks-wise it could resemble an alligator snapping turtle, with a three-ridged shell, thick legs with large claws, and a large head armed with a formidable razor-sharp beak.