Depends on what youre talking about.
Over all nuts and bolts, covering every catagory, I would easily put WEBE as the top signal. WEBE *used* to be a normal catch in the Springfield area before that LPFM signed on up there, it is easily listenable in Manhattan, it carrys well through New London, and even heading out Rte 6 towards Willimantic, you get it before WXKS takes over. What is amazing about WEBE is the fact it's mounted to the side of the united illuminating stack. That 6 bay, half-wave spaced antenna just rocks.
The West Peak Non D signals (WWYZ, WZMX and WDRC) , the Avon Mountain signals (WTIC-FM, WCCC), Rattlesnake Mountain (WRCH), all do very well for "corner to corner" coverage. I've always contended that WPLR's signal outdoes WKCI's, with the exception that WPLR has a lot more interfering factors on it's fringes. WKCI's signal is still a monster, weither it is better now than it was when it was on the WTNH tower is also up for debate.
A station not mentioned here , who has a very impressive in-state signal is WRKI. WRKI's signal does very well north and south, and to the west. It really is limited to the east by the terrain, but still does really well.
An honorable mention HAS to go to WJMJ on 88.9. For a B1 from Johnnycake Mountain, it does very well too.