Tip: A common level trope to avoid is "item babysitting". This involves forcing the player to carry P-Switches, springboards, or other items all around the level. Usually, this doesn't end up being very fun or engaging, so use another level gimmick if you can.
I see. Some people still might use more than one, though (for instance, ZSNES for most things but SNES9X for Earthworm Jim 2 and Super Mario RPG, or bsnes for most things but ZSNES for old broken hacks). I guess you did say "favorite", though.
Also, I use no$sns, but if it doesn't work, I get out my time machine and go grab a copy of higan 0.97.
I'm a bit weird. I debug my stuff (mostly) on snes9x143 (its fastforward makes it easier to get anywhere), but for playing anything (both hack and official game), I use bsnes (070 compatibility). I also keep s9x152 around because it has RAM watching, and bsnes080 for compatibility testing.
There are far too many emulators.
-------------------- <blm> zsnes users are the flatearthers of emulation
While I wholly support bsnes and it's mission, I still voted for snes9x. bsnes has some nice things, but byuu is not a UI designer and he doesn't care about the user. I have never even been able to get the newest versions of bsnes to run any games (haven't tried that hard). The newest version of snes9x is safe enough for the light gaming I do (that which I don't do on the snes, meaning my testing the rom to make sure it works), and the fast forward feature works much better than bsnes' same. I still use bsnesd for debugging (an old version usually, newer if I'm doing something particularly clever), but snes9x just has the corner on usable emulators that actually work.