Pocket kings. It's the second-best hand in hold'em, which means folding the hand before the flop isn't entirely out of the realm of possibility — in theory, anyway.
If you've been following the relaunch of Poker After Dark on PokerGO, you know how that very topic came up, and immediately a situation presented itself in which a player with pocket kings genuinely had to ponder whether or not to let his pair of kings go before the flop.
The stakes were $400/$800 and the stacks quite deep.