For a great night out if you are in South Tenerife (excursions are organised if you want a drink) it is worth a trip to the Castillo San Miguel for the Medieval night. It is not actually a bar, but a purpose built castle, just off the Autopista Sur at the Los Abrigos exit.
The show is tremendous with falconry, horse dressage, jousting and sword fights taking place, soup is drunk straight from the bowl and food is eaten with your fingers. Wine and soft drinks are provided free and beer available by the jug for 5 euros.
Afterwards you go to another section of the castle where you can meet the Knights and watch a show (last week it was a Drifters tribute show but I believe this may change at various times throughout the year)
Well worth the 40€
Dave