I'm of the very small minority that considers Episode I the best of the prequels, so I have a soft spot for it.
Me too. Despite all of its flaws, I like TPM the most. I was only eleven years old when it came out and remember it more fondly than the other prequels, plus it's bearable as a stand-alone story. What I like about it I like a lot, in fact:
1. Overall feeling. It was very different in style to the OT, yet it's the only prequel that felt alien and fantastical like the original movies; I still can't quite point out whether if it's due to the camera work, scale models, or exactly because it's so different, but it feels more like Star Wars than the other CGI prequels.
2. Visual and audio design. Love the locations (Naboo's core being the exception) of TPM, the vehicles, droids, costumes, props and spaceships. TPMs CGI looks quite outdated today, but its composite effects hold incredibly well. N-1 starfighter, AAT tank, even the "donut" battleship, excellent sci-fi designs. A nod to the audio effects, the vehicles just sounded great.
3. Liam Neeson's Qui-Gon Jin. If there was a Jedi I could relate to as an actual character rather than nameless action hero with a glowing baseball bat in the prequels, that was him. Ewan McGregor's Obi-Wan is great, too, but his performance is better in AotC and RotS (one of the few things that are better about them). Anyway, any scene with both of them in it is quite fun and well acted.
4. Random action shots. The initial assault on Theed, blaster firefights in the palace corridors, all of the few space battle scenes without kid Anakin*, the escape from Naboo, droids deploying for battle/droid invasion. And all scenes with Qui-Gon and Obi-Wan fighting, especially the Duel of the Fates.
5. Duel of the Fates - deserves own mention.
6. Darth Maul. Best prequel villain, although I would have loved to see Christopher Lee in an extended role. His count Dooku could have been an excellent Separatist equivalent to moff Tarkin throughout the entire prequel trilogy, instead of just two short (and pointless) lightsaber duels. They would have made an excellent combo as the physically strong and cunning villains in the long run.
7. The soundtrack. Best among the prequels, I can still hum many of the themes by memory.
8. Ian McDiarmid. Excellent performance in a poorly written role. I wish he had a bit more time in TPM. I preferred his sleazy manipulation then outright villainy. Oh, wasn't he just slimy...
9. Watto. Proof CGI comic relief characters can work.
That's about it. I can point out random things from AotC and RotS like individual designs, locales, music cues etc., but nothing as coherent and important as in TPM.
*no offense to Jake Loyd, not his fault really.
EDIT:, Hm, I guess I should add Jango and Obi-Wan's confrontation too. Both the stand-off and the actual fight on the rain, on the platform. It was well executed, plus I've always wondered how a regular soldier would perform against a Jedi in the movie.