Loukili (sp?) at 50's Prime Time is awesome. We always have some great servers there, but Loukili is the best. We will purposefully ask for Loukili (and have learned that he usually works a later shift, so it's best to schedule for after 4pm).
On our last trip, we missed Loukili's shift, but got a server named Kim who was a riot as well. At first we didn't think she'd be much fun, but she turned out to be a blast.
Also, it's been awhile since I've seen him there (so he may be gone), but Will, a Servant of the Beast (as he introduced himself) at Be Our Guest was great.