"K".
K? K what? The letter
before L? The letter after
J? Did you know that in
"JK", the K stands for
"kidding", so your reply is
"kidding"? K as in
Potassium? Do you need
Special K for breakfast?
K, as in can I k/o you?
Can I knock you out then
feed you to the hungry
sharks? Sharks has a K in
it!