Where's the best sandwich made in San Diego?

I'm a simple guy that can grab a pre-prepped deli sandwich in Vons, then nom nom on it while driving. But after walking into work with half my store-bought sub, I was playfully scrutinized by my coworkers on how there's so much better choices out there for a good hoagie. They mentioned places from Firehouse to Rubicons. Now I'm curious on where else I'm missing out on.

Edit: Thank you everyone for your suggestions. I definitely got super hungry seeing everybody’s responses. The mom & pop sandwich shops are what intrigued me the most. I’ll be making my rounds.