Self admitted envelope filter/synth fan here.... I feel like there's a there are a couple envelope/filters out there that I've also tried but am not remembering for my list below, but here are my top favorite filters.
@kesslari mentioned earlier in the thread that it would be helpful to have a full list for context, so I've included that as well.
I fell in love with the Pigtronix EP2 quite a few years ago, but that thing is a chonker, so I was pretty thrilled when the Bass Envelope Phaser was released. The BEP has easily been my hands down favorite ever since, by enough that I have a spare like @drumsvsbass mentioned since it's been discontinued. I guess I just find the combination of envelope and phaser to be pretty magical.
Line 6's Auto Filter and the Proton are often tied for second. The filter in the Helix sounds great and has a ton of controls (modeled after the Lovetone Meatball), with the option to add some gain/grit. All versions of the Proton have always been good, simple to use, thick sounding envelope filters.
The XeroD and Proton could be tied for third depending on mood... The Proton is easier to dial in, but Taylor's filter has expression control for
killer manual synth style sweep control on anything you feed into it.
The Filter Twin has the characteristic Aguilar warmth with some really interesting flavor of both filters active at the same time.
Honorable mention goes to the Barge Concepts Grinder. I deeply regret selling that one and would love to track it/one down again, but they're so rare they're non-existent. It was another one based on the Lovetone Meatball, and I was pretty early in my filter/effects pedal explorations at the time, and was in over my head with it... so I mistakenly passed it on.
5sg.
My personal top filters
1) Pigtronix Bass Envelope Phaser
2) Line 6 Helix Auto Filter or 3Leaf Audio Proton V4
3) Proton or Iron Ether Xerograph Deluxe
4) Aguilar Filter Twin
The Full list
3Leaf Groove Regulator
3Leaf GR2
3Leaf Proton v1
3Leaf Proton v2
3Leaf Proton v4
Aguilar Filter Twin
Ashdown Bass Envelope Filter
Ashdown Funk Face v1
Ashdown Type 23
Barge Concepts Grinder
Boss AW-2 Auto Wah
Digitech bass synth wah
Digitech Dirty Robot
DOD FX25
DOD FX25B
DOD440
Earthquaker Spatial Delivery
EBS Bass IQ
EHX Micro Q Tron
EHX Dr Q
EHX Qtron+
EHX Enigma
EHX Bassballs Nano
EHX Bassballs Russian
Ibanez AW7 Autowah
Iron Ether Xerograph Deluxe
Line 6 Auto Filter
Line 6 Tron (Up/Down)
Line 6 Asheville Pattern (Moog MF105M)
Mojo Hand Analogue 442 Red
Mr. Black Fwonk Beta
Mutron III Haz
MXR M188 Bass Auto Q
MXR M82 Bass Envelope Filter
Pigtronix Bass Envelope Phaser (the small white and purple one)
Pigtronix EP2 (the big blue whale one,
modded by Dave Koltai with a volume knob)
Pigtronix Bass Envelope Phaser
Source Audio C4/Spectrum
Source Audio Manta
Subdecay Prometheus v1
WMD Fatman
Xotic Robotalk 2
Zvex Seek Wah