When I worked in the restaurant world, four strong and simple effects I did were:
Jokers Wild - (Penguin id- it need a new routine that is a little more engaging, but even if you just used that routine, it is a short, flashy effect, that demonstrates skill, involves two-three spectators, and quickly establishes your credibility as a magician.
The almighty TT. - I always had a silk appear and vainish. Simple, but powerful to laymen, and like the above trick, flashy, and establishes that you are good at what you do. -That and you can do a bazillion other things with a TT (Well, maybe not a bazillion...)
Sponge balls - I personally feel, it is such a wise thing to carry a couple of sponge balls with you as a restaurant worker. If you are working in a place that does not have many families, then they are perfect to bring out-kids love them. That said, adults go nuts over them! Some of the loudest reactions I get are from sponge balls (I think simply because they seem to 'jump' out of their hand - that makes people excited
). And they are fun to perform as a magician.
One more that I always did was a prediction effect that I came up with, where I dealt card onto the table and the spectator said stop anywhere. The card they stop at matches the prediction exactly. I just saw that Jay Sankey has what looks like the EXACT same trick on his site - He calls it Stop Sign, and it looks like hes got it free on his site-crazy! I do the same idea, but with cards (as for the prediction, I just write it down, or I will use the 'matching' card from the deck (same color and value but opposite suit). - I like this effect because it is a little bit of easy mentalism, and now I combine it with a version I created where they then repeat the effect, but they shuffle first, they deal out the cards, and they turn the card over- I never touch the deck. The prediction is in an envelope and is a card from another deck - the spectator can even open the envelope. It makes for a nice routine, and works every time.
justin