One Piece Chapter 29, page 7-9: Slopes

Nami asks where Luffy is, and Usopp explains that Luffy ran ahead so fast he lost sight of him. They realize Luffy must have gotten lost. Usopp tells Nami to charge ahead while he covers her, but Nami refuses, pointing out that she is weak too. Usopp admits he is shaking in fear and can't even move his legs, though Nami suspects he's lying. Meanwhile, the pirates are ignoring them and talking amongst themselves.

Jango orders his crew to charge and destroy the village. The pirates rush up the slope with weapons raised. Usopp suddenly remembers he has caltrops (spikes). Nami eagerly grabs some from him. Together, they throw the spikes onto the slope to slow the charging pirates down. The pirates step on the spikes and scream in pain.

Zoro is running up a steep, muddy slope, panting heavily and cursing Nami for tricking him. He slips and slides back down, but catches himself. He steels his resolve, drawing his swords, and runs up the slippery slope with incredible speed, shouting "UWOOOOOH!".