To pick one is very hard. Every bike I've ridden has given me some special memories.
For me probably the two main stand outs have been the CB125TDC and the VFR750.
The CB125 was brilliant because I had just sold the Yam RS125, which was a dog. The CB felt like a refined big bike.

It had electric start, twin exhausts, four stroke engine, 12v electrics and felt solid when you rode it. Maybe it just felt so good because the RS had been so awful. I didn't really get to have a full summers worth of riding on it but the few months that I did get, were superb.

The VFR750 has been the bike which has taken me everywhere. For a bike that is 13 years old, its in pretty good condition. I remember the day I saw it in the bike shop, the old XBR had been in for an MOT and I was hanging around waiting for the results. I spotted this big red machine in the window and knew it had to be mine but I didn't really have the cash. In the end, it was the wife that said I should go for it. She took one look at the bike and said, you really want it, don't you.

The rest is history.
The bike is great. Its fast, it handles (although the rear shock is pretty tired), and its never let me down when I've been out. It may have protested a few times but its always got me home.

When you open it up, the roar of the exhausts is something special. It doesn't really kick you in the pants, it just accelerates hard, all through the rev range.
Its given me memories of trips to Cambridge and Scarborough and also trips up north through Glen Coe with the lad on the back and getting caught in some of the worst rain imaginable. Then stopping at Arrochar for a cup of tea and a sandwich or maybe riding down past Loch Eck. My earlier bikes contented themselves with the occasional trip to Largs but the VFR has really opened up my options.
For me, the VFR has probably been the bike and the good thing is, I still own it.