In pokemon black,I've checked all of Route 1 , but all i found was,
Lillipup, Patrat Lv.2 - 5!
There are no wild level 1 anywhere in the wild. However, you can get them by hatching an Egg. The Pokemon that hatches out of an Egg will always be at level 1. If you have a level 1 Pokemon in another game, you can use the PokeTransfer to transfer a level 1 from D/P/Pt or HG/SS, or simply trade with someone else for a level 1 Pokemon.
You could hatch an egg. Also I believe Regiggas Is at Lv. 1 in D/P (Dont know about platinum). Not sure if that helps though.