Especially for drums or short percussive envelopes I really like the old (and cheap) Doepfer A-142-4 Quad Decay. Sure it's decay only, but sometimes that will do just fine. A little harder to track down, but worth it for the amazing EG/HP ratio is the Bubblesound HEXa(s)r. The envelopes are all on the short side (something like a max of around 4s or so per stage) but again, lots of applications where a full ADSR is overkill. For more complex envelopes I love the Xaoc Zadar. My favorite classic ADSR is the Roland 540, but I guess the Frequency Central clone System X Envelope is just as nice.