I am a huge fan of Frankie's.
Some friends and I went here on a spontaneous trip and now it's one of my favorite bars to go to. We usually start around 7pm or so because it can get pretty packed. We were there on a Wednesday and it filled up with people nicely. It is important to note that they are open 24 hours.
The tiki themed decor is fun and on Fridays if you go wearing a Hawaiin shirt, your first drink is half priced. However, the prices are already really reasonable which makes going here an easy decision.
Frankie's is not kidding about the skull ratings on their drinks. If it's a five, it is very potent (and delicious). So be warned. There's not much in the way of food around the bar so be sure to eat before you get there. I would definitely recommend this place to anyone who likes drinking and rum at reasonable prices.