Jamie’s Guitars:
1994 Fender Squier Series Stratocaster (1 of 2)

When Jamie joined the band, this was still in original condition, but was ultimately modified to resemble one of Kurt Cobain's guitars. This included a replacement neck with a rosewood fretboard (the original, maple board neck wound up on Chris' Frankenstein Super Strat), a Seymour Duncan Hot Rail bridge pickup, and the replacement of the trem screw under the low 'E' with a sheetrock screw. That last detail was discovered when Jamie and Chris went to the Hard Rock Café in Boston to analyze the smashed up remains of one of Kurt's Strats.

Pictured here before the mods.
1994 Fender Squier Series Stratocaster (2 of 2)

This is the exact same model as the last one, just a different color and left unmodified; in fact, he bought both guitars at the same time. Often the face would be graffitied with slogans like "I ❤️ noise" or "live man/dead man", but these would always rub off and then get erased via lighter fluid (and occasionally fire).
Sometimes, if he knew he was going to have a particularly expressive performance, he would switch to this one since his violent onstage outbursts might damage the black guitar.
Chris would also periodically use this onstage, and the one time Aaron ever played guitar in public it was on this instrument.
1968 Fender Mustang

This was not Jamie’s guitar, belonging to the band’s roommate, Allison Brennan, but Jamie was quite fond of it and used it whenever she would let him. Strat pickups were installed and it was given a metallic blue paint job by a previous owner, so in the era that these were becoming collectable, that made it considerably cheaper due to it not being 100% vintage spec.
Chris added a Seymour Duncan ‘59 humbucker to the bridge position per Allison’s request, though in the above photo it still has the Strat pickup.
While it cannot be confirmed, Jamie very likely used this to track some songs on More., given his affinity for it.
Mid 70s Hohner HG07

This was the guitar Jamie played most at home, though it can be heard on some of the Boston era demos and a handful of songs on More. A pickup from an Kawai hollowbody and the associated controls were added to give it an "Unplugged in NYC" vibe, which was useful for the acoustic sets played by Jamie's Nirvana tribute band.
Jamie’s Effects:

Pedals are shown loose; they were eventually mounted to a piece of plywood.
Boss TU-12
A simple analog tuner, used by all three guys in the band but anchored to Jamie's board.
DOD FX75B Flanger
This would be the third one of these used by an Amoeba. There is no evidence that Jamie ever used this on record.
Boss DS-2 Turbo Distortion
Made famous by, you guessed it, Kurt Cobain, it's the more saturated version of the iconic orange distortion pedal, and is heard prominently on lots of songs.
ProCo Rat
Previously used by Mike and then given to Jamie because Chris really disliked the sound of the DS-2. This was Jamie's main distortion sound on More.
Boss CH-1 Super Chorus
Because you can't do grunge if you don't get that underwater sound.
Boss RV-3 Reverb/Delay
Like his flanger, there is no evidence that Jamie turned this on while the tape was rolling, but Aaron and Chris made extensive use of it on their four-track demos to get reverb on drums and vocals.
Jamie’s Amps:
Crate PA Head (probably a six or eight channel)

In case it isn't obvious, Jamie was a huge fan of Kurt Cobain, and even adopted his cheap gear ethos. He wasn't really interested in finding the perfect amp, and this worked fine.
1989 Mesa Boogie Studio 22 Preamp (similar model pictured)

Of course, fate can intervene and the perfect amp can find you.
Legendary as the heart of Kurt's rig, this showed up one day in Daddy's Junky Music's bargain basement. The guys had a habit of cruising the music stores in Boston on their days off, and the bargain basements at Daddy's and Wurlitzer yielded some great finds. This was easily the crown jewel, and Jamie wiped out his bank account to buy it without a moment's hesitation.
Oddly, there is no evidence that it was ever used on stage, perhaps for fear of damage or theft.
Sunn Concert Lead Head

A preamp is pointless without a power amp, and when the PA head died unexpectedly, a new amp was required. This was chosen from the Wurlitzer bargain basement simply because it was smaller, cheap, and had a jack labeled "power amp in", therefore taking the worries out of how to connect it to the preamp.
Given that it was a 200 watt amp that sounded decent by itself, it was used that way at gigs, though when combined with the Mesa Boogie, it was Jamie's sound for More.
Electro Voice 1x15” Cabinet (pictured above)
All variations of his amp rig fed this cabinet.
Like his PA head used as a guitar amp, this was re-appropriated from its original intent as a bass cabinet, and was likely purchased on discount.
Strings and picks:
Dean Markley 9-42 electric, no preference for brand but 10-47 acoustic
Dunlop Tortex .60mm standard