Top Gun is right about Bagel Cafe for deli.
On Spartan's recommendation, I tried Holstein's. Was not disappointed. I love an Angus cheeseburger cooked medium rare. They're hard to find unless you go the $20 burger route.
Vegas has a lot of cheap - and good - Mexican restaurants. No need to spend big money eating Mexican. I've had some of the best Mexican at dive-type places.
As far as steaks, no way to get off cheap if you want a great one. My favorite steakhouses are Delmonico's at the Ventian and Del Frisco's just off the Strip.
When it comes to pizza, I like thin and greasy. If that's your style, I would recomend Aurelio's. It's a chain that orginated in Chicago. There's just one left in Vegas - and it's in North Las Vegas. Worth the drive, though, if you love that kind of pizza. Metro Pizza is very overrated. Naked City pizza isn't. It's excellent. Pizza Rock is good, too, but pricey.
One of the great things about Vegas is you can find just about any ethnic restaurant and they usually are good.
Vegas has some excellent Thai restaurants. Lotus of Siam is legitimately famous. Tourists go there. It's definitely good. But my favorite is Wera Thai on West Sahara. Excellent lunch specials.
Best coffee shop restaurant is Jerry's Nugget. It's in North Las Vegas, but worth the drive. Affordable and great-tasting prime rib there along with fantastic cakes. They have a huge menu and everything I've tried has been good, including an excellent tuna melt.
I'm happy with Bonefish Grill for fish. Surprising they also make a great burger there as Hitman will attest to.