1) i'd put bitmixer on top of them all because it is the oldest mixing service around (started in 2014-1-10 on the forum)

2) any online exchange or gambling site can be used for this as long as they are legit places and you are comfortable with using them. and the only benefit is that this method is super cheap but the downside is that they will keep logs. so it is only good for regular people who don't mind that.

3) this method is a bit complicated and i have never personally done it but it is done using a second coin (Monero) you change bitcoin to XMR and this altcoin offers anonymity and then (there may be an step here) you change it back to bitcoin. you can use shapeshift or any exchange for this.