As almost everyone else has already said, definitely Hydrocodone or Oxycodone. Codeine to a lesser extent, although for me it's more just 'not sedating' and warm and fuzzy as opposed to stimulating. Kratom takes the cake, but that's not an opiate really, more of a quasi-opioid. Personally, I've always found Bupe to be the most sedating, more so than Heroin, at least when I was opiate-naive. I remember IV'ing 4mg of Subutex after being clean for 23 months and I was literally sucking my own dick for 36 hours... felt great though.
I've also heard Nalbuphine is relatively stimulating, or again at least not very sedating. It's very hard to find now, but completely legal. Bodybuilders were using it frequently in the early 90's to work out with harder and push past their pain tolerance (till most got addicted to other opioids, a lot on heroin..). Since they were lifting hardcore on it, I couldn't imagine it was very sedating. However, idk what ROA you prefer, but if needles ain't your thing neither is nalbuphine, cos the only form I've ever seen it sold in is IM/IV ampoules, although I suppose you *could* drink the amps. I just don't know how much of a hit in terms of bio-availability you'd take by consuming it orally, and since I've *never* seen it sold orally, I'm gonna go out on a limb and guess that it's oral BA is pretty weak.
Also, Nalbuphine is a mixed agonist/antagonist so IDK how combining it with other opioids would work, if at all.