I'm still using my Microsoft Intellimouse every day and I have another, brand new one, sitting in my "spares" cupboard.
tried others but none of them are as comfortable to hold and I always go back to my little oldie
[My Belkin KVM caters for 4 computers and allows for a combination of UBS and
PS/2 - which is wonderful !!]
I also have an ancient "sit up and beg" keyboard with back feet that can be raised up and fabulously clanky keys
[And I have a brand new spare of that, too !! I really don't like the "sit flat on the desk" types with silent key operation.]