I've flown a decent range of them, but two definitely rise to the top as my "favorites":
* Featherweight Raven.......ultra capable of just about anything I could ever want in an altimeter, unbelievably tiny (especially considering all the features this thing has), couples with FW AV bays and Perches (with integrated switch) which are awesome in their own respect, super high quality. Due to it's combination of features and form function, it simply does things no other option can do.
Downsides?.....it's pricey, and unfortunately since Adrian got so busy with other things in life, his support, while good, isn't as "completely awesome" as it used to be.
All things considered, if I had to choose "just one", it would be a Raven.
* Missileworks RRC2+.....far and away the best value in altimeters today. Great price, super user friendly and easy to use, it's nice and compact, great quality, just enough features and functions to meet my demands but not lots of extras/bells & whistles/etc. that might get in the way. If you want a simple altimeter to just do the main job of most "regular" flights, but you want high quality, this can't be beat. And Jim's support IS "completely awesome".
Downsides?.....really the only thing would be more advanced features, but if you want that it's an easy step up to an RRC3 (which is not all that much more expensive).
If I'm on a budget, but don't want to sacrifice quality, or I'm looking for a great "bread and butter" altimeter, this is the one to choose.
The other altimeters I've flown and really liked (honourable mentions), and can wholeheartedly recommend are:
* Missileworks RRC3 (mentioned earlier)
* AltusMetrum Telemini (another like the Raven that is minscule, and does things nothing else on the market can do)
* Perfectflight Stratologger
* Adept22...no longer made (I believe) and filled that niche that the RRC2+ does now (and does even better).
s6