I just looked through all sugimori’s card arts and wow, 90% of those are some of the most uninteresting basic design cards ive seen. I was hoping for something that showcased a little more but was more unique than red’s pikachu. I settled on Fieldworker
For non-tcg, i would have a poster professionally printed of either of these arts for him to sign, but preferably pikachu looking like a science experiment.
I have fond memories of fieldworker!
So that or Erika’s Ivysaur, I remember staring at this card for hours as a kid.
Postcard
I don’t think these are done by sugimori I think they’re done by itoh
That makes more sense, i wasn’t sure about it since they kept coming up for sugimori but arent in his style. I’d still have him sign them for additional weirdness.
TCG card:
Non-TCG:
Tbh, any non-TCG Seviper item with Ken Sugimori art would be fine, but it’s funny and unique to have him autograph these tissues.
Honorable mention (it’s neither a TCG card nor a non-TCG item 
):
Greetz,
Quuador
A homie with exquisite taste. I also love sugimoris’s sentret drawings.
I see some really interesting replies!
There’s a reason why many of you would ask to sign a trainer card instead of a Pokemon creature card?
It’s because you don’t like that the Sugimori “style” for Pokemon cards is a “stock” artwork with a generic background instead of a complete illustration?
Honestly I also think that many of you could change idea if they got only 1 opportunity to get a card signed and have to choose between a card that could pay their retirement cost or a card that holds only a sentimental value (even if the Sugimori signature would add financial value even to a common card)