There are a shitload of anonymous sushi restos in the Annex and you're going to have to travel west to hit real gold. Ever since discovering this place I haven't been able to eat at other sushi restos without feeling like I'm being unfaithful. This place is the shit and they sill remain stubbornly modest.
I run the risk of sounding cliched when I say this but I'll do it anyways. The atmosphere at Mazz is great. You walk in and a cheerful server welcomes you. Their servers are always happy and accommodating. You now have a choice between their standard tables and the big wooden party room. If your party is big enough, take the room. You will not be disappointed.
Everybody seems to be talking about quality, authentic sushi nowadays. I have a feeling that you can't find that stuff anywhere outside the land of the rising sun so I've settled for good ol' north american-style sushi. This place has good (good, not great, good) sushi. The menu is huge, with several pages of rolls, sashimi and sushi combos. Freebie appetizers always come before the meal. The mains are all Korean and Japanese barbecue dishes with a smattering of udon bowls and plates and the standard bento boxes. This place is great because you can stuff your face full of sushi for under $12.
If all that didn't convince you, here is one more tip. The take 15% off your total if you pay in cash.