Depends where you live.
I live in Gilwell halls, when I leave it I have 3 options. Straight ahead is a bar called The Skiving Scholar, they are more of a rock/heavy metal type place and sometimes have a band in the basement playing.
I can go left and there is 2 bars that I come across in about 30 seconds of walking; Blush and Ride, both are pretty classy with ride having a huge out door area like a front garden. Blush is rather small but classy. If I continue about 20 seconds I get to The Roundabout, this is a very good pub and is pretty big (2 floors) you can get good deals here and with a yellow card you can get discounts. I could continue walking and reach voodoo bar but I have yet to go in here so cant really comment about it. I could go round the roundabout to the bac bar, which is a small bar but always packed for some reason.
The right option is more appealing to me, 30 second walk and you come across 2 bars; Cuba and Firefly, both are very good. Cuba is pretty popular and some nights it can get packed. There is polls to dance on and a free bottle of something if a girl gets up and takes her top off. Firefly isn't really as famous but its good to, both bars have an upstairs and an outside garden. I can turn right again and about 30 seconds down I reach Fresher & Professor, another legendary student bar which is always good, mainly for its signature drink the "terminator" which is what 70% of people in that place must order. Its a very nice cocktail served in a pint glass, you wont really think its an alcoholic drink until half an hour later because its pretty strong.
I could also turn left from them 2 and reach the SU bar in about 2 minutes. I think its one of the best SU bars, its where most students here start there night. Friday and Saturdays it is very popular and is open much later. Monday night is exchange night and prices change depending on what people are buying, so the drinks no one is buying are extremely cheap, usually drinks like snakebite. I managed to get a shot of something for 30p.
Inside the SU you have 5 main rooms, the 1st is the 1st main bar and has large television screens and lots of seats and tables, there is the snack shop room where you can get food there or if you prefer a more lit up area, or quite area. The next room is where most of the pool tables are, its the 2nd largest and has around 4 pool tables, it also has a good dance floor which on a Friday or Saturday night will be lively, it has a DJ booth there. There is a smaller room with another bar but its only open on busy nights, the last room is the biggest and it contains the sub:lime bar and a huge dance floor, a big projector which has sport during the day and music videos and stuff. It also has 2 pool tables and more tables and chairs closer to the bar, it also has a dj booth.
There is a vodka revs near, about 15 minute walk to get there. Vodka revs isn't really a club its more of a very big bar but its worth going. There are many places near by and a lot of food places, some pretty big bars near revs. There is also C103, which is a club and its pretty big however some of the tables and stuff are a bit messed up but the dance floor is huge and its very lively with a few bars to buy drinks from (it might take a long time getting a drink on some nights)
Oceana is the main attraction for night life in plymouth, its the largest club I have been in so far and they do themed nights and so on. I think its more popular with the girls then the boys. You can get a free bus there on its student night (monday) from SU bar. A lot of people go there so go early to get in.
There are other areas like near the barbican, which has many traditional pubs and a few bars. I remember going to a pretty big weather spoons there. Also a lot of royal navy pubs there.
I am just a fresher though :P there is lots of places I need to go to.