data = {{1, 2}, {2, 7}, {3, 14}};
newData = data /. {x_, y_} -> {x, 1/y}

newData = Cases[data, {x_, y_} -> {x, 1/y}]

f[{a_, b_}] := {a, 1/b};
newData = f /@ data

{#[[1]], 1/#[[2]]} & /@ Data

{#, 1/#2} & @@@ data

Replace[data, {x_, y_} :> {x, 1/y}, {1}]

data /. {x_, y_} -> {x, 1/y}

Cases[data, {x_, y_} -> {x, 1/y}]

{{1, 2}, {2, 7}} /. {x_, y_} :> {x, 1/y}

{{1, 2}, {1/2, 1/7}}

dat = RandomReal[99, {50000, 2}];

Do[ {#, 1/#2} & @@@ dat , {50}] // Timing

Do[ Transpose[{#, 1/#2} & @@ Transpose@dat] , {50}] // Timing