I'm kinda partial to the old Omega D2's with the variable condenser. Solid construction, widely sold, and suitable negative carriers/lenses out there for just about any format from 110 pocket films up to 4" x 5" sheet films. I started as a kid with the inexpensive Omega B-22 (which itself will handle 120 negatives up to the 6x6cm square format) but the D2 is the last B/W enlarger I'll ever need.
This is what I use as well. It covers all of my formats, is mechanically simple, and was very inexpensive.