The best thing I've ever heard ATC say was something I was involved with.
In April, during my never-ending PPL course in Dayton at Delta Connection Academy (for various reasons out of my control, it's taken a year), my instructor and I went up for a review flight. We flew out to the practice area & did slow flight, Power-Off & On stalls & other performance maneuvers. We then planned to go back to the airport, take a break & go back out to do pattern work.
On the way back into Dayton, we called approach & told them that we'd be returning for a full stop. They assigned us runway 18, which we headed toward. We were told to maintain 2,500, which was unusual. About 5 miles northwest of the runway, my instructor (I was flying) looks out the window & yells "Holy sh*t!! There's two A-10s below us!" It took me a second to remember what an A-10 was, but when I did, I jerked my head to the left & was wide-eyed when I saw the fighter looping around below us.
Immediately after this, my instructor, angry because we weren't told about the traffic, calls approach & says something to the effect of:
Inst.- "Dayton approach, Cessna 39W has the traffic in sight."
Appch- "Cessna 39W, roger."
Inst.- (agitated) "So you want us to avoid the A-10s, then?"
Inst.- "Ok, how many are there?"
...at which point, I held up two fingers, as I had seen a second one fly under us. ATC then confirmed that there were two out there. We continued to both fly & watch them, laughing & surprised at what we'd just seen. It's something that's probably common with WPAFB being there, but neither one of us had seen anything like it. We even started quoting lines from Top Gun, like "I WANT VIPER." The best line came as we were handed off to tower:
Appch- "Cessna 39W, report the airport in sight."
Me- "Field in sight, 39W."
Appch- "Cessna 39W, traffic no factor, cleared straight in runway 18, contact Dayton Tower 119.9....
Don't hit the 'hogs."
A310/319/320/321/333, ARJ, BN2, B722/73S/733/734/735/73G/738/739/744/757/753/767/763/764/777, CR1/2/7/9, DH6, 328, EM2/ERJ/E70/E75/E90, F28/100, J31, L10/12/15, DC9/D93/D94/D95/M80/M88/M90/D10, SF3, SST