Hmm.
In Pathfinder, three spring to mind.
1) Homebrew campaign. My elven fighter and the rest of the group were participating in a gladiator style fight. We were due to go up against a team from the noble house we hated the most, one who happened to be responsible for the war of humans and elves that had seen my character's kind largely wiped out. We had been taunted by them previous to the fight, and public knowledge was that they were fierce fighters. Well, they didn't anticipate my potion of Enlarge Person and an elven fighter standing 10 feet tall wielding a glaive the size of a small tree tripping them and causing all sorts of mayhem with several attacks of opportunity. We utterly destroyed them, and my character, never one to let a sweet victory go to waste, used some of the victory money to commission a statue of me with the glaive in the courtyard right in front of their manor.
2) This was in RotRL. Our party was having some trouble figuring out how to transport everyone over the walls of a certain mountain fortress in Book 3. I was playing an elven druid, and had the idea of wildshaping into a Quetzalcoatlus and flying everyone over on my back. The GM shot down that idea, saying that I could not wildshape into that form because I had not come from an area that had those. I said "Fine, I prepare the Sky Swim spell and wildshape into a killer whale." Cue looks of confusion on the fort inhabitants' faces as an orca swims across the sky with a squad of adventurers on its back...
3) Same game as above. We had gotten word there was going to be a certain catastrophic flood that was powering through a valley. Rather than take the long way around, I had my druid turn into a water elemental and said "I am going to surf the flood" as I position myself on top of the massive wall of water.
First thing that comes to mind, I talked about here.