(;AB[pj][nk][pk][qk][pl][om][on][po][pp][oq][qq][qr][rs]AW[pi][qi][qj][rk][ql][pm][qm][qo][qp][rq][rr]C[Black plays.

Source:
    Problem #23 from the yose volume of Gokyo Seimyo, a nearly 200 year old problem set.

Analysis:
    Myron Souris]SZ[19]
;B[qn]C[The wedge tesuji here makes White's shape amazingly awkward.];W[rn]C[White has no choice but to block here, or Black would take this point next.];B[ro]C[Now Black makes White pay for leaving behind so many cutting points.]
(;W[rp]C[White can try to save all his stones, but ...];B[rm]C[... Black cuts again.]
(;W[rl];B[sn];W[pn]
(;B[rn]C[Hugh Zhang and Teddy Terpstra correctly pointed out that this move in the original solution does not work!];W[sp]C[And Black loses the semeai.])
(;B[sp]C[Black starts a big ko for the entire corner.]
(;W[sr]C[Makes White's situation even worse.];B[rn]
(;W[sm];B[sl];W[sk];B[rj]C[Now the ko is even bigger for Black.])
(;W[sl];B[rj];W[ri];B[qs]C[Black wins the semeai.]))
(;W[rj]C[Fails];B[rn]C[Black wins the semeai.])
(;W[sm]C[An internal ko threat.];B[sl])))
(;W[so]C[White can make life in the corner, but ...];B[rl]C[... Black captures 3 stones, in addition to ruining most of White's side territory.]))
(;W[pn]C[White could capture here ...];B[rp]C[... but then Black captures the corner stones in gote.]))