If you don't have bags, head directly to LAS T3. The cab line there is shorter on nearly any day any time. Sure it's about $4-5 more due to T3 being further away, but it's very worth it to avoid wasting a whole hour at the T1 line
another weird trick is the car rental center. if the line to the car rental bus isn't too long, take that bus for a 7 min ride over to the rental center. there's a line of cabs waiting at the rental center, and never a line.