Well I have to say that I have a number of favourites. My favourite Leopard would have to be 172 (VOI 172) of Coleraine. Another big favourite of mine is Tiger 1172 (MXI 3172) of Londonderry, especially in its days as an all over advertisement for Tango. It always put a smile on my face when I travelled on 1172. Up here there is not as many advertising buses as in Belfast, so a bus like 1172 stands out more. When you got a trip on 1172 people noticed you and everyone would wave at you.
I am also a big fan of Tiger 1272 (OXI 1272). 1272 is a very quick bus and a very nice bus to travel on.
I would also agree with Paul about the TXI Cityliners. One example I know well is 1343 (TXI 1343) which is now at Newtownabbey ( ex Magherafelt Goldliner). 1343 is a very comfortable bus - alot more comfortable than any of the 1500 or 1600 Goldliners I think, but like most other Ulsterbus buses are now getting on in years.