Cubes I own or have owned:
Moyu Weilong GTS2
Gan 356 Air UM
homemade Gan 356 Air M
homemade Valk 3 M
Moyu Weilong GTS
Rubik's brand 2.0 3x3
old Rubik's brand
Moyu 13x13
Cubicle Wushuang M
Qiyi Wuque
Cyclone boys 4x4
Cyclone Boys 3x3
bad stickerless megaminx
Rubik's 360
WitEden Oskar Mixup cube
Qiyi square one (low modded)
Yuxin 5x5
bad stickerless 5x5
Rubik's keychain cube
Yuxin White 2x2
Yuxin Blue 4x4
Mirror cube
Rubik's brand 2.0 4x4
My favorite cubes (I don't necessarily have them):
GAN 356 Air SM
Price: $30.55 at cubezz.com
This 3x3 has a smooth and soft feel, while maintaining great stability and speed. This cube is magnetic so with every turn the layers gently click into place. This cube also features a better magnet mechanism; the magnets are placed in little compartments inside the peices so that they don't fall out and you can replace them with different strength magnets if you want to. All in all, this cube has proven to be very good, setting two world record averages so far and is used by many of the top speedcubers. Most people who get this 3x3 end up using it as their main cube.
Qiyi Wuque M
Price: $53.99 at thecubicle.com
This cube has a silky smooth, heavy feeling. It has good corner cutting and is very stable. If you're looking for a great 4x4 that won't pop, lockup or corner twist at medium-tight tensions, then this is the cube for you. The reasonably strong magnets in this cube give it much higher stability compared to the non-magnetized version. it also holds both single and average world records for 4x4.