Again, since they dont require specific colors, theyre very flexible
Cards like Igneous Elemental really excite me
Selvala, Explorer Returned Besides being an elf, which is already interesting for typal purposes, Selvala, Explorer Returned can generate between 0-4 mana any time you activate its ability

Sort Card Type Blastoise & Piplup GX #38Ultra Rare $79.69 Blastoise & Piplup GX - 016/064 #16Double Rare $29.31 Blastoise & Piplup GX - 069/064 #69Super Rare $32.95 Blastoise & Piplup GX - 070/064 #70Super Rare $299.99 Blastoise & Piplup GX - 076/064 #76Hyper Rare $74.50 Blastoise & Piplup GX (Alternate Full Art) #215Ultra Rare $458.33 Blastoise & Piplup GX (Full Art) #214Ultra Rare $85.00 Blastoise & Piplup GX (Secret) #253Rainbow Rare $119.59 Piplup #93Common $2.23 Piplup #15Common $23.98 Piplup #15Common $17.54 Piplup #85Common $4.29 Piplup #16Common $9.64 Piplup #121Common $4.77 Piplup #27Common $1.99 Piplup #33Common $2.86 Piplup #RC6Uncommon $14.41 Piplup #36Common $0.63 Piplup #54Common $0.31 Piplup #93Promo $2.79 Piplup #35Common $0.24 Piplup #25Common $0.66 Piplup #8None $6.22 Piplup #18Common $2.71 Piplup - 003/066 #3Common $5.44 Piplup - 004/066 #4Common $4.13 Piplup - 009/049 #9Common $0.57 Piplup - 027/094 #27Common $0.13 Piplup - 042 #42Promo $11.68 Piplup - 052/049 #52Character Rare $75.60 Piplup - 098/094 #98Illustration Rare $14.12 Piplup - 20/25 #20Promo $1.03 Piplup - 2007 (Akira Miyazaki) #93Common $3.67 Piplup - 32/156 (Toys R Us) #32Promo $38.34 Piplup - 71/100 [Platinum] #71Promo $26.28 Piplup - 72/100 #72Promo $2.00 Piplup - 93/130 (Cosmos Holo) #93Promo $44.92 Piplup - 93/130 [Diamond and Pearl] #93Promo $27.70 Piplup - DP03 #DP3Promo $26.27 Piplup (15) - 2008 (Dylan Lefavour) #15Common $15.70 Piplup (31) #31Common $0.38 Piplup (32) #32Common $0.92 Piplup (71) #71Common $1.90 Piplup (72) #72Common $6.14 Piplup (72) - 2008 (Dylan Lefavour) #72Common $10.50 Piplup (DP03) - 2008 (Dylan Lefavour) #DP3Promo $18.46 Piplup (Secret) #239Secret Rare $72.47 Blastoise & Piplup GX (Alternate Full Art) #215Ultra Rare $458.33 Blastoise & Piplup GX - 070/064 #70Super Rare $299.99 Blastoise & Piplup GX (Secret) #253Rainbow Rare $119.59 Blastoise & Piplup GX (Full Art) #214Ultra Rare $85.00 Blastoise & Piplup GX #38Ultra Rare $79.69 Piplup - 052/049 #52Character Rare $75.60 Blastoise & Piplup GX - 076/064 #76Hyper Rare $74.50 Piplup (Secret) #239Secret Rare $72.47 Piplup - 93/130 (Cosmos Holo) #93Promo $44.92

For me the apex of that is in Serra Angel
Recommended For You Currently sitting at a premier market price of $50, this double-character glimmer commands the highest price tag of any standard base card in the expansion