The Entertainment District is packed with bars, pubs, restaurants. I gravitate to sports bars and pubs. Three that I remember are the Loose Moose, Duke of Argyle and Elephant & Castle. But there are a bunch of others scattered around.
If you mean bars with DJs, etc. there are tons on Richmond St, Adelaide St which are also in the Ent. District. Most that I saw had VIP lists with people lining up outside, which isn't my thing (especially when I knew there was hardly anyone inside). But supposedly there are some great DJs there.