DJ Ruckus -- Best Wedding Gift Ever ... Me!!! (PHOTOS)

DJ Ruckus headlined a very special wedding ... for free.

Ruckus' friend/publicist, PR guru Amanda Ruisi who runs AKR Public Relations got hitched in Florida to banker Robert Sorrentino at the fancy schmancy St. Regis Bal Harbour.

Ruckus -- whose +1 was fiancee Shanina Shaik -- surprised everyone when he DJ'd the party well past 2am.

A set by Ruckus usually goes for $75k .. so free is definitely a bargain.