Off the top of my head:
-UNI 2.0 or RTS Cyclonus (depending if you like G1 toy or cartoon colors)
-RotF Ejector...a little killer toaster
-RTS Lugnut
-ENER or 25th Anniversary Unicron (the colors)
-Armada Megatron...a big electronic green tank, with a bit more play value and articulation compared to G2 Megatron
-ENER Galvatron...it's G1 homages galore. Plus it's a big jumbo piece of plastic with a funky space jet/cruiser alt mode
-Generations Scoop...can't go wrong with a figure with 2 Targetmaster guns
-Prime Wheeljack...futuristic sports car with decent articulation and 2 non-rubbery swords
-Generations Swerve...very good little figure
-Generations Starscream (Legends)...decent crossover between G1 and modern jet. I love the colors, and it comes with a little Waspinator if you liked BW.
-PCC Undertow....an excellent figure. There's not that many waterbased alt modes for the Decepticons
-Animated Arcee...not perfect, but a very good homage.
-Animated Rodimus...a very good figure that's almost 100% show accurate.
-Cybertron Scrapmetal (any color)...I just love both modes. The key activated feature is kinda crappy, so you can ignore it.
-RiD Scourge...if you like a good toy that was also on the show. Plus it's a legit black Optimus, not some repaint to sell a toy.
-Armada Mini-Cons...there are a variety of teams to suit your preferences. Some have been released in multiple colors as well. The Japanese ones might get pricy, but some have better color schemes.
Your tastes may differ from mine, so do research first on my list above. There are plenty of galleries of each figure.