Here is a list of known Gnutella clients (dead and alive):

Code Name
---------------------
BEAR BearShare
CULT Cultiv8r
GNOT Gnotella
GNUC Gnucleus
GNUT Gnut
GTKG Gtk-Gnutella
HSLG Hagelslag
LIME LimeWire
MACT Mactella
NAPS NapShare
OCFG OpenCola
OPRA Opera
PHEX Phex
QTEL Qtella <------ here
SNUT SwapNut
SWAP Swapper
TOAD ToadNode
XOLO XoloX
ZIGA Ziga

See:
Registered vendor codes http://wilm.nl/gnutella/wiki/ServentVendorCodes
GDF Database (registered users only, stupid) http://groups.yahoo.com/group/the_gd...tAt=&prntRpt=1

PS: As far as I know the vendor codes should be treated case insensitive (I think for example Bearshare uses/used different writings of BEAR, a kind of version sheme). As you see all vendor codes are a 4 character code, new clients can use 4 spaces as temporary name.