Smith Morra Gambit
As black, I always accept the gambit, and usually win. Just don't take the b2 pawn, because if you do, white will blitz out attack, and black will be severely hobbled by his own lack of mobility.
A lot of white players will play the Smith-Morra Gambit because they're working under the assumption that black will take the b2 pawn, giving white a huge advantage in mobility, and white will dominate the diagonals from the a1 to h1 corner, and adjacent diagonals.'
It more or less equalizes for black to ignore the b2 pawn and just make developing moves.