@susanooooWell units that are useless in 1v1 are those, that have a huge weakness in at least 2 lvls. Stuff like phantoms, komodos, pandas, engis and such. Prolly the best units period are ygg and ea, LoD and aqua are also awesome.
For a practising, just start a map in single player and after picking the mode, type -debug, there you can do various stuff, like:
every unit you send will be sent on your lane also
-ikw to make your king invincible,
-clear to kill all the creeps,
-level X to change level,
-spawn X to toggle desired spawns for creeps,
-start to immediately start the level,
-gold X, -lumber X, -income X (self explanatory),
-p to pause, -r to resume the game...
Those are just commands that come to my mind, i'm sure there's more.