I love the Horseshoe! It's one of my favorite music venues in Toronto and it's by far my favorite place to go to shows alone. The dark bar, low ceilings, and pillars make it cave-like with plenty of places to lean and drink your bottle of 50 without looking like a loser, really just the opposite!
I've seen some amazing shows here including Death Cab For Cutie, Bright Eyes, and many many others.
The bar is well-equipped with washrooms, the beer is decently priced, the bartenders have been there for years and are extremely friendly, and the door guy is as great as they come. The Horseshoe is the CBGB's of Toronto, but with a much friendlier disposition!