Had the Treo (Palm Pilot + Cellphone) because I worked a job which had multiple appointments per day, and the calendar and notes were essential.

Absolutely loved it, even though it was half-way outdated from new. They broke easily, though, and the cellular functionality was buggy as all hell - like, really bad and so very often just quietly not working so you'd be missing calls and have no idea.
Eventually moved to a Samsung with a keyboard but missed the efficient UX of the Treo, and the charm of graffiti.

Also enjoyed a Sharp Zaurus like another guy in the comments did (Linux-based PDA with a keyboard!).

And a Psion 5a! - Absolutely fantastic little machine, with a remarkably good keyboard and decent resolution for the day. I just wished it had been DOS compatible as well for some basic have and tools.

Later, I had some sort of Early PocketPC running what I think would have turned into Windows CE?

And earlier than any of these, various little Sharp databank things (basically a calculator screen and a keyboard, used for not much more than phone numbers and addresses, really - 1-4kb storage) including a real early one which was only a touchscreen!

The touchscreen one deserves more of a mention because it was rectangular, like a layer, and had clearly visible perforation-like marks across the screen in a grid pattern.

The touch was purely pressure-based and though it came with a stylus there was no actual freehand input of any sort, it was basically just a tiny finger to press the distinct segments of the screen which acted like buttons. Like a constantly changing keyboard, really, as what was under each segment changed according to what you were doing.

Still had no more effective functionality than the other PDAs of the time, but looked and felt so much more futuristic. Loved it!

Gadgets used to be so different from one another.