I have an Akai MPK mini that I like a lot. Smallish, but still decent sized keys. Plus some pads and knobs that are easy to map into Renoise (i.e. split the Akai output so that the pads trigger percussion while the keys do something else.)
I also have a Novation Launchpad, an older model (now discontinued) that I rarely use.
I seem to prefer normal piano-style keyboard entry. The QuNexus from Keith McMillen gets a lot of use as well. Pretty compact, great when there's limited space or when travelling.
The Reloop looks slick, sort of like the MPK but with expanded pads.
You'll have to sort out how you plan on using Renoise, how many pads you'd want, size of piano keys, durability/reliability, etc.