Mechanically, the only way to 'hold' a creature is a grab.
Grabbing just immobilises the target, and you can take an action to 'try' (making a strength attack) to drag the target.
That's the only legal interaction. (short of utility powers, the Fighter power Forceful Drag for example lets you.... drag the creature without having to make the Str attack)
So as far as rules go, without going into powers since the latter are allowed to override the rules, no.
The only time I have seen a creature being used as a weapon is by the Cave Troll (DMG 157) who can grab and then make a special attack harming both a target and the grabbee, and even then a Troll is at least one size category larger than a PC. (Large versus Medium/small).
So, houserules. I have a player taking the role of a (relatively large) Gnoll Fighter-Brawler. We have agreed that he can use a standard action while grabbing a creature of a lower size category to fling it at a target, using athletics checks and nebulous math.
Picking up and wielding/hurling a creature of your size wouldn't be believable until the players hit Epic where one almost expects one to beat someone over the head with their comrade, though by then it would be unlikely to be more effective than using magical weaponry. (if not, then the magical weaponry is clearly lacking)