At my store, too many players draft Boros from too few packs and split all the good cards among equally poor decks while I have my choice of everything Dimir. It usually ends up a couple open Boros bombs while the newer players keep drafting R/W without real support and don't notice packs going around with multiple playable U/B/G cards.
Modern: (G/U)Infect (G/U)Tron
Legacy: (U/B)Tezzeret (U/B)(W/U)Miracles(W/U)(B/G)Dredge(R/W)
Commander:(U/R)Mizzix (U/R)(W/U)Sydri(U/B)(W/U)Zur(U/B)