OK. I do not think I got it correct, and I may be wrong, but I'll try to answer, because who doesn't try anything doesn't get anything as well.
If I understand, you want a Sneasel with Ice Punch and Assist, not you ?
OK, try out this: (Pokémon Black and White 2 mandatory)
- Catch a Female Sneasel.
- Get a Female Furret.
- Get a Male Liepard with Assist.
- Breed Liepard + Furret. Baby Sentret should be Male, and knows Assist.
- Make Sentret evolve, and learn Ice Punch to your new Furret from the BW 2 tutor.
- Breed Sneasel + the new Furret = Sneasel with Assist and Ice Punch :)
This is the best way I've found to get Ice Punch and Assist Sneasel. Then, transfer the Sneasel to X&Y (I think PokéBank is now open, but trust me, I do not know.)
If you already have a female Sneasel with Assist and try to get one with Ice Punch as well, then I do not think there is a Pokémon which learns both Assist and Ice Punch by level up. The method I listed above is, I think, the best one to get a such Sneasel.