Squirtle, i'm just not feelin it
Piplup, because is pretty and when the Dawn (Lucinda, in Italian)'s Piplup rolls down on the anime episodes, he's very funny! XD
Oshawott because they are horrible battle pokemon
Totodile. But I find all the Johto starters to be pretty "meh" as a whole.
My least favorite Water-type starter is Blastoise. It has a somewhat decent design on its FRLG artwork and in some of its early sprites, but unfortunately it looks ugly in most of its other sprites, artworks and specially in the anime (seriously, it is SO overweight in the anime). Its mega evolution is quite ugly as well. I don't hate it, though, I think Blastoise is a nice starter Pokémon, it just happen to be my least favorite of all them. In regards of Water-type starters, imo: Feraligatr > Samurott > Empoleon > Swampert > Blastoise.
I do like Swampert's unique typing for a starter, but I do have to say that overall the Mudkip line is my least favorite. There really isn't anything about their designs I find particularly appealing (they aren't bad designs, just not among my favorites).
I also can not stand Dewott's design. But then it goes and evolves into Samurott which is easily my favorite of all starter final stage evolution designs, so it easy to overlook.
Totodile - sharp guy=)