We've all seen the center fork trick:
White gets the pawn back and restores material equality. Black has achieved the goal of eliminating white's central e4 pawn.
Here is a new one to me (from a blitz game):
This position just came up from a Grunfeld I was playing. It was a blitz game, so I just trotted out Nbd7.
1. ... Nxd5 !? eliminates white's center completely!
Obviously 2.Qxd5 Bxc3+ wins the queen, so 2.Nxd5 is the only try.
And here is what I call the center pin trick's follow up
2. ... Be6
The knight is pinned to the queen and lost. White can cash in with 3.Qxc7 Bxd5 4.Qxd8 Rxd8 for material equality.
Black has a slight pull (White will have to untangle quite a bit.) , but the pawn structure is very drawish.
The whole variation has just served to eliminate white's cramping d5 pawn.
I only give Nxd5 an !? because the final position may not be enough for black if he is playing for a win. It equalizes at least however and gives black a good, playable position.
Anyway, capturing a pawn that was twice protected never even occured to me!
It's a nice trick to have in the arsenal for future reference!