Well, I'll start.
Canadian General Electric
"Grooveback"
Common in Toronto, Mississauga, Brampton and around the GTA. Their numbers have been steadily decreasing over the years though mostly because of LED and pole replacements. Was probably as common as the Fortran poly back in the 90s
"Novalux"
VERY RARE, only Prescott is still known to still use them. Toronto used to have them with STOP-CAUTION-GO worded lenses as seen in some old archival photos from the 1930s. Not sure when they removed the last of them.
Automatic Signal/LFE
Aluminium
Uncommon, but Mississauga and Vaughan still have a few that's hanging on.
Poly
Occasionally seen in Toronto and in York Region
Econolite
Bullseye
Rare Only Brampton and Belleville is known to have them..
Buttonback
Somewhat common on older installs in Oakville
Current Aluminium Model (For lack of a better name)
Somewhat common on mid-late 2000s installs in Oakville
Bubbleback Poly
Somewhat common model, used mainly for spot replacements though.
Crouse Hinds
Type D/DT
VERY RARE not sure if any are still in use. Seen in some old archival photos of Toronto.
Type M
VERY RARE but there's a 12-12-12-12 one scheduled for removal at 401/Islington. a 8" beacon might still exist as the Hwy 6. north/401 onramp.
Type R
Hard to find, only seen in Toronto. A 8-8-8 version also existed but they were removed in 2010.
McCain
Aluminum
Seems the be the current signal of choice in Halton Region.
Poly
Some have popped up in Hamilton recently
Optically Programmable Unit
Used in place of the 3M Light, somewhat rare
TCT/PEEK (poly)
Have been used in place of the similar looking Fortran model in some new installs and spot replacements. Sometimes seen around the GTA
Eagle Signal/Siemens
Flatback
Some still remain in Belleville and maybe in Toronto. The 427 had a bunch of them at the ramps until recently. Oshawa has one still use.
Mark IV
Somewhat common on older installs in Oakville and in Mississauga
Alusig
VERY RARE...never actually found any examples still in use but I've seen them listed on Kiijii in the Ontario style 12-8-8 with yellow backplate configuration which makes me think they were used here at one point.
Durasig
Common in York Region
Fortran Traffic
Aluminium (looks almost identical to a CGE)
Common in the same places that have a ton of CGEs...basically the same model
Poly
Very common all over the GTA
Northern Electric
"Ornamental Eaglelux"
VERY RARE, I don't think any are still in use in Ontario.
"Rodded Light"
VERY RARE, but Belleville still has a few as of 2011.