This game is taken from the popular "Musical Chairs" birthday party game.
There are two ways to play this game. For young players (4-5 years old), I recommend that you start each player dribbling within a defined area (about 20 x 30 yards). When you yell "Switch", the players leave their ball where it lies, and then scramble to find a new ball (one left by another player). Everybody finds a new ball and nobody is knocked out.
For older players, the game can be made a bit more challenging. Use cones or discs as "home bases". The trick is that there aren't enough home bases to go around (i.e. with 12 players set up 10 home bases). Your players dribble around, and when you yell "Go Home", players scramble (with their ball) to dribble to (and claim) a home base. Only one player is allowed per home base. Whichever player doesn't find a home base has to complete a small challenge (5 jumping jacks, 5 knee-jumps, etc.). Be sure to encourage players that have to complete these challenges by applauding their effort, etc.
To add to the challenge, remove more home bases. Challenge your players to practice moves while they are dribbling around.
Finally, if you find players hovering around a home base, tell them it isn't allowed and if they keep it up they'll automatically have to do the challenge. Even better, set up the home bases in a separate part of your practice field away from the dribbling area. When you call out "Go Home", players have a fun race in front of them!