Not on the strip, but Pink Taco at the Hard Rock has good happy hour deals. Half off appetizers, and 2 for 1 Margaritas. I think the hours are 4-6 M-F. The appetizer platter there is $7 during happy hour, and enough food for 2 people.

At the fashion show mall,
Cafe Ba Ba Reeba has $3 tapas, and half-off alcohol 4-7 every day, and 4-Close Fri-Sun. $12 1.5L pitchers of Sangria is a killer deal. Also, if you're a Wynn employee you get %40 off anything not on happy hour there and at Stripburger.

If you want drinks and are between Flamingo, and the Venetian, Casino Royale has cocktails somewhere around 3 or 4 dollars all the time. They also have $1 beers, and $1 Margaritas but there's usually a huge line for them.