The 'strange' aspect can be the context it was recorded in, or the actual sound recorded.. come on - weird me out!
Took cave tour in Arkansas and the tour guide was talking about how he could play "Greensleeves" on the stalactites, the pitch was so pure. I arranged a private tour later that week for recording. Turns out he was exaggerating. There weren't enough of the right notes for that song, but there were plenty of pure tones. I recorded my samples, took them home and did some pitch correcting and eventually sent him a copy of Greensleeves on stalactites.
Ooooh, well, hehe...As much as I hesitate to even admit this, I record myself when I'm sick. I got some amazing phlegmatic goodness during one bad cold (I sounded like an Orc), and some very strange things recording my gut with a hydrophone used as a contact mic when I had food poisoning (sounded like...well, I don't know what. It sure was weird!).
No, I don't record myself actually being sick. I'd make myself ill just listening to it!
I would have to go with Baby ostriches. Boy do hey make a crazy sound. I was ask to go record adults hooting . . . sort of make a guttural sound, but the babies make this weird trill like chirp:
One of my strangest must be the recordings I made of a broken toilet that produced plenty of interesting noises after you flushed it. It banged, rattled, whizzed and whirred. The funny thing is that it wouldn't stop - once you flushed it, it just went on like this for ever., until you messed around with its pump to make it stop.
You can listen to a snippet here... Not sure if SSD accepts the Soundcloud player as an embedded object, but here goes:
I'm not answering the question because this wasn't a recording of my own, but made by a classmate of mine. I've heard the recording a couple of times and I think it's worth well telling.
This classmate (Claas) was recording a bell of a railroad crossway in the middle of nowhere when a guy suddenly walked up to him and tried to ask him something. Claas putted his finger on his own lips to silence the man, cause the train was coming and the bells were about to start ringing. All of a sudden the unknown man ran up the railroad towards the train. You can hear the train honking in pretty close distance and then putting all his powers on the brakes. You can hear my classmate screaming in panic. And you can hear the unknown mans footsteps running in distance.
Fortunately the train stopped just in time.
The unknown man ran away and my classmate tried to follow him in the woods but couldn't find him anymore, he's still trying to figure out what the man asked him before he started ranning towards the train.
It's by far the most creepy thing I've ever heard and will hear.
Tried to freeze a microphone into a puddle overnight so I could record people iceskating over it the next day. Mic didn't live through the night. :(
Successfully stuck a contact mic onto our cat's belly and got a good 30 minutes of purring footage, which was later turned into the sound of a much larger beast type animal, with surprisingly little processing. :)
This question actually caused a dream last night and then prompted a blog post:
Tim, thanks for triggering a funny memory.
I fisted a silicone vagina. (I feel like that's going to get flagged, but it's the honest truth... I really need to post that sound.)
Here's the question I posted about it (slightly NSFW) Weirdest thing you've ever done for sound
I managed to sneak my Zoom H2 onto "Tower of Terror" ride in Disney World in Tokyo! The recording sounds really eerie since I haven't a clue what's being said in Japanese by the narrator but it did managed to scare the life out of me! It was a bit of a challenge keeping hold of my Zoom as I plunged down the tower!