Beauty is in the eye of the beholder. There would be as many top 5's as there are CMDRs. To put my Cr 2:
Number 5
the Adder
Smaller and younger brother to Challenger Space Shuttle or slightly used soap bar with wings. You decide. Adder reminds me of every day delivery van from the '80s - bulky in shape but with sleek lines. At least it's not a hand axe (prehistoric stone tool, fyi) like Sidewinder or Cobra.
Number 4
the Diamondback Explorer
Cricket. Grasshopper. Space Bug. You either love it or hate it. What is sure - you won't pass it unnoticed. Still looks like an ice sculpture made with a blunt machette, made by drunk fisherman. But it has tilting engines. Tilting engines.
Number 3
the Python
Sitting quietly in the bushes, the hunter observed his prey. Slowly, not to disturb surrounding twigs, he pulls out a single arrow from the quiver. He charges his bow, taking careful aim. Holding his breath he...
"CMDR, this is station's flight control, you are free to proceed to landing pad number 43."
... releases the string and slips through the mail slot. Straight to the point. This is Python.
Number 2
the Imperial Eagle
Jet. Space jet. If you ever wanted a jet, not a flying brick (not that shape in space matters...) like T-series or anything Federal or a duck stone like anything Lakon, iEagle is your only choice. Mandatory white.
and finally, my top spot goes to...
surprisingly
Number 1
ez equo
the Imperial Clipper and Imperial Cutter
You may say it's space Jumbo Jet. You may laugh their wings and nacelles. You may mock their cockpit shape and front window. It's jealousy, no need to hide it. Cipper/Cutter are an iMac among PCs, pinnacle of design fetish. If your middle name is "Style" then you won't pick anything else. They may be other ships that perform better. But none does the job more elegantly than these two.
No wonder both are rank restricted. Only truly chosen ones are worthy enough to pilot them.