Slinky is Woody's best friend among Andy's toys. He's also one of the toys that stays the most loyal to our cowboy hero—just as dogs are man's best friend, toy dogs are toy man's best friend.
In the staff meeting scene, Slinky helps round up the other toys and then chimes in to agree with Woody during key parts of his speech. He's got faith. If Woody says things are going to be okay after Andy's birthday party, well, that's good enough for Slinky. He also believes Woody when he tries to tell the other toys that the whole pushing-Buzz-out-the-window incident was an accident. But, here, Slinky's the only one feeling the Woody love.
In the end, Slinky even risks overstretching himself to save Woody and Buzz as they try to race into the moving van. He's obviously a super-loyal, super-friendly, and super-kind toy. Good dog!