(Some of these are groove boxes that I use as drum machines, but w/e)
Roland TR-707 - Bought it new a long time ago. Don't really use it much these days, but back in the day I could make it sound pretty interesting by running the individual outputs into EQs and separate outboard effects.
Roland TR-8 - I wanted a hardware synth that emulated the 808 and 909. It does the job.
Roland TR-8S - Just bought the 8S and will probably sell the 8. Great drum machine.
Behringer RD-8 - It's more the realization of a dream than a necessity for me. I always wanted a true analog 808. It's fun to use for live remixing and beat creation, etc.
Electribe ER-1 - Not a ballsy drum machine by any measure, but fun for minimalist setups. Back in the day (late 90s) it was pretty much the only hardware drum synth on the market.
Electribe EMX - One of my favorite drum machines / groove boxes overall. Great sound presence. Probably the best kick sounds of any ROM based hardware drum / groove machine.
Electribe ESX - Ditto.
Yamaha RM1X - More of a sequencer than a drum machine, but I've coaxed some low-fi good stuff out of it over the years. Great art happens within limits.
Boss DR-202 - I bought this back in the late 90s before I got an MC-505 and still like it. It has just enough of everything (including a built in bass synth) to be fun and useful. Runs on batteries too.
Roland MC-505 - Fun for making 90s club style music. It's a bit dated, but that's the point. Built like a tank.
Electribe 2 - Love the sound and portability, kind of hate the interface.
Ensoniq ASR-X Pro - I use it mostly as a sampling drum machine, even though it does a lot more.
Roland MC909 - IMO Roland's best groove box/drum machine to date. I like it much better than the MC707 even though they're almost 20 years apart. This thing is a powerhouse.
Maschine Studio - Technically Maschine is a lot of things, but even as a drum machine it's in a class of its own because of the sound library, Drumsynth, and the quality and responsivity of the pads.
Roland TR-08 - Fun little drum machine for noodling around with live remixing setups before the RD-8 was available. No individual outs for different parts, but still fun to play with.
Roland TR-09 - Ditto.
Arturia DrumBrute - I had higher expectations for this drum machine, but it's still decent. Just don't expect it to be a 909. Sounds really good when sync'ed with something ballsy like the EMX or MC909.
E-Mu XL7 w/MP7 ROM added - Surprisingly good as a drum machine, though it does lots of other things. I love the bank of knobs. Very playable and tweakable. E-Mu was onto something and then they were bought up and shut down.
Yamaha AN200 - I bought this as a synth because I always wanted the AN-1X, but ended up liking it more for the drum sounds. They sound REALLY good.
Yamaha DX200 - Ditto. Surprisingly powerful FM synth, but not a lot of fun to program even with the software. It's great as a drum machine with FM to add digital sounding bass or bleep/blop sound effects. It really shines when MIDI'd with other groove boxes.
Yamaha RS-7000 - Probably my favorite hardware unit for making rhythm tracks, though Maschine, EMX, and MC909 are a close tie for second. The RS has its flaws (poor SCSI implementation and hard to find Smart Media memory cards) but the internal drum sounds and master effects are great for inventive live remixing.